Abstract Aim: To evaluate the antifertility effect ofAlstonia scholaris bark extract in male rats. Methods: In male Wistar rats Alstonia scholaris bark extract was given by oral route at a dose of 200 mg/day for 60 da...Abstract Aim: To evaluate the antifertility effect ofAlstonia scholaris bark extract in male rats. Methods: In male Wistar rats Alstonia scholaris bark extract was given by oral route at a dose of 200 mg/day for 60 days. The fertility and testicular function were assessed by mating tests, sperm motility, sperm concentration, biochemical indices and testicular cell population dynamics. Results: Oral feeding with the extract at a dose of 200 mg/day for the period of 60 days did not cause body weight loss, while the weights of testes, epididymides, seminal vesicle and ventral prostate were significantly reduced. The production of step-19 spermatids was reduced by 79.6% in treated rats. The population of preleptotene and pachytene spermatocytes were decreased by 61.9% and 60.1%, respectively. Spermatogonia and Sertoli cell population were also affected. The seminiferous tubule and Leydig cell nuclear area were reduced significantly (P<0.01) when compared to the controls. Reduced sperm count and motility resulted in a total suppression of fertility. A significant fall in the protein and sialic acid content of the testes, epididymides, seminal vesicle and ventral prostate as well as glycogen content of testes were also noticed. The fructose content in the seminal vesicle was lowered whereas the testicular cholesterol was elevated as compared with the controls. The following compounds were obtained from the extract with chromatographic separation over Si-gel column: α-amyrin, β-amyrin, lupiol acetate, venenative, rhazine and yohimbine. Conclusion: At the dose level employed, Alstonia scholaris bark extract has a significant antifertility effect in male rats; the primary site of action may be post meiotic germ cells (Step 19 spermatids).展开更多
A stability indicating LC method was developed for the simultaneous determination of Amlodipine and Benazepril capsules in pharmaceutical dosage form. Efficient chromatographic separation was achieved on Symmetry C18 ...A stability indicating LC method was developed for the simultaneous determination of Amlodipine and Benazepril capsules in pharmaceutical dosage form. Efficient chromatographic separation was achieved on Symmetry C18 stationary phase with simple combination of amobile phase containing 750 mL of DI Water, 250 mL of Acetonitrile and 2 mL of Octylamine into suitable container with adjusted pH to 2.50 ± 0.05 with the aid of Ortho phosphoric acid delivered in an isocratic mode and quantification was carried out using UV detection at 240 nm at a flow rate of 1.0 mL·min-1 with an injection volume of 20 μl and ambient column temperature. This method is capable to detect both the drug components of Amlodipine and Benazepril in presence of their degradation products (Amlodipine Imp-A and Benazepril Impurity-C) with a detection level of 0.05%. Amlodipine/Benazepril in their combination drug product were exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the samples were analysed. Peak homogeneity data of Amlodipine and Benazeprilis were obtained using PDA detector, in the stressed sample chromatograms, demonstrating the specificity. The method shows excellent linearity over a range of 0.05%-2.0% for Amlodipine, Amlodipine Impurity-A and 0.05%-5.0% for Benazepril and Benazepril Impurity-C. The correlation coefficient for Amlodipine and Benazepril is 1. The relative standard deviation was always less than 2%. The proposed method was found to be suitable and accurate for quantitative determination and the stability study of Amlodipine and Benazepril in pharmaceutical preparations. The developed HPLC method was validated with respect to linearity & range, accuracy, precision and robustness.展开更多
Transition metal-catalyzed decomposition of diazo compounds and subsequent transformations constitute vast synthetically useful reactions. Recently the catalytic approaches to ylide generation and reaction leading... Transition metal-catalyzed decomposition of diazo compounds and subsequent transformations constitute vast synthetically useful reactions. Recently the catalytic approaches to ylide generation and reaction leading to heterocycle compounds from diazo compounds have achieved remarkable successes.……展开更多
A new bimetallic complex containing Zn and La was prepared from a salen ligand possessing methoxyl groups at the 3, 3′-positions. The structural feature is that one of nitrate groups is disordered and displaced betwe...A new bimetallic complex containing Zn and La was prepared from a salen ligand possessing methoxyl groups at the 3, 3′-positions. The structural feature is that one of nitrate groups is disordered and displaced between two metal centers. Crystal system: Triclinic space group:P-1, Z=2. a=0.82714(17) nm, b=1.3484(3) (1) nm, and c=1 3898(3) (1) nm, α=79.89(3)°, β=76.67(3)°, and γ=72.43(3)°. V=1 428 6(5) nm3, Dx=1.812 g·cm-3. (Δρ)max=1 510×10-3 enm3, (Δρ)min=-1.503×10-3 enm3. Accordingly, two water molecules occupy the metal centers in the apical positions via the syn-geometry.展开更多
The objective of this study was to improve primary-amine nitrogen (1°-N) quantification in dissolved organic matter (DOM) originating from natural waters where inorganic forms of N, which may cause analytical int...The objective of this study was to improve primary-amine nitrogen (1°-N) quantification in dissolved organic matter (DOM) originating from natural waters where inorganic forms of N, which may cause analytical interference, are commonly encountered. Efforts were targeted at elucidating organic-N structural criteria influencing the response of organic amines to known colorimetric and fluorescent reagents and exploring the use of divalent metal-assisted amide hydrolysis in combination with fluorescence analyse...展开更多
Peptide side-chain conformations, especially the aromatic side-chain residues, play an important role in the molecular recognition processes between peptide ligands and their corresponding receptors. The modificat... Peptide side-chain conformations, especially the aromatic side-chain residues, play an important role in the molecular recognition processes between peptide ligands and their corresponding receptors. The modifications on peptide side-chain can result in biological activity changes and many other property changes. β-alkyl constrained α- amino acids have been applied for peptide molecular design, and have resulted in some important results in peptideresearch in recent years.[1～3]……展开更多
It has long been known that the configurational isomers of biologically active compounds, e.g., nutrients, pesticides, and drugs, may exhibit different activities in a chiral environment such as the human body. Althou...It has long been known that the configurational isomers of biologically active compounds, e.g., nutrients, pesticides, and drugs, may exhibit different activities in a chiral environment such as the human body. Although the majority of drugs presently in development are chiral, analytical and preparative methods for the quantitative determination and purification of stereoisomers still lag behind. One reason is that commonly used chiral selectors for the direct resolution of enantiomers are not tailor-made for a specific analyte. The identification of suitable selectors for a particular pair of enantiomers still requires considerable experimentation and is generally demanding with regard to material, time and labor. The rational design of chiral host molecules, therefore, represents a challenge in facilitating enantiomer analysis. In this article, we describe how a combination of techniques ranging from organic synthesis to molecular biology yields antibodies of predetermined specificity and stereoselectivity that can be used as tailor-made chiral selectors for the chromatographic separation of enantiomers and their sensitive detection in immunosensors.展开更多
Conducting polymer, polyaniline （PANI）, has been studied as a novel electroactive and electrically conductive material for tissue engineering applications. The biocompatibility of the conductive polymer can be impro...Conducting polymer, polyaniline （PANI）, has been studied as a novel electroactive and electrically conductive material for tissue engineering applications. The biocompatibility of the conductive polymer can be improved by （i） covalently grafting various adhesive peptides onto the surface of prefabricated conducting polymer films or into the polymer structures during the synthesis, （ii） co-electrospinning or blending with natural proteins to form conducting nanofibers or films, and （iii） preparing conducting polymers using biopolymers, such as collagen, as templates. In this paper, we mainly describe and review the approaches of covalently attaching oligopeptides to PANI and electrospinning PANI-gelatin blend nanofibers. The employment of such modified conducting polymers as substrates for enhanced cell attachment, proliferation and differentiation has been investigated with neuronal PC-12 cells and H9c2 cardiac myoblasts. For the electrospun PANI- gelatin fibers, depending on the concentrations of PANI, H9c2 cells initially displayed different morphologies on the fibrous substrates, but after one week all cultures reached confluence of similar densities and morphologies. Furthermore, we observed, that conductive PANI, when maintained in an aqueous physiologic environment, retained a significant level of electrical conductivity for at least 100 h, even though this conductivity was decreasing over time. Preliminary data show that the application of micro-current stimulates the differentiation of PC-12 cells. All the results demonstrate the potential for using PANI as an electroactive polymer in the culture of excitable cells and open the possibility of using this material as an electroactive scaffold for cardiac and/or neuronal tissue engineering applications that require biocompatibility of conductive polymers.展开更多
Pyrrololactam type of alkaloids was found in many marine sponges which belong to the family Axinellidae. In the course of our systematic research for bioactive substances in marine organisms, we studied the sponge Pha...Pyrrololactam type of alkaloids was found in many marine sponges which belong to the family Axinellidae. In the course of our systematic research for bioactive substances in marine organisms, we studied the sponge Phacellia fusca Schmidt which also belongs to the family Axinelldae. From the chloroform-soluble fraction, ten A-nor-sterols were isolated and identified, while from the water-soluble portion, three known pyrrololactam alkaloids and a new pyrrololactam alkaloid, which was named fuscin, were obtained. The present paper contains the isolation and structure determination of fuscin (1).展开更多
A wide variety of different types of microorganisms are known to produce intracellular energy and carbon storage products, which have been generally described as being poly (β-hydroxybutyrate), PHB, but which are, mo...A wide variety of different types of microorganisms are known to produce intracellular energy and carbon storage products, which have been generally described as being poly (β-hydroxybutyrate), PHB, but which are, more often than not, copolymers containing different alkyl groups at the β-position. Hence, PHB belongs to the family ofpoly (β-hydroxyalkanoastes), PHA, all of which are usually formed as intracellular inclusions in bacteria under unbalanced growth conditions. Recently, it became of industrial interest to evaluate these PHA polyesters as natural biodegradable and biocompatible plastics for a wide range of possible applications, such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such 'tailor-made' copolymers can be produced under controlled growth conditions in that, if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.展开更多
The quantum nature of bulk ensemble NMR quantum computing the center of recent heated debate,is addressed. Concepts of the mixed state and entanglement are examined, and the data in a two-qubit liquid NMRquantum compu...The quantum nature of bulk ensemble NMR quantum computing the center of recent heated debate,is addressed. Concepts of the mixed state and entanglement are examined, and the data in a two-qubit liquid NMRquantum computation are analyzed. The main points in this paper are: i) Density matrix describes the "state" of anaverage particle in an ensemble. It does not describe the state of an individual particle in an ensemble; ii) Entanglementis a property of the wave function of a microscopic particle (such as a molecule in a liquid NMR sample), and separabilityof the density matrix cannot be used to measure the entanglement of mixed ensemble; iii) The state evolution in bulk-ensemble NMRquantum computation is quantum-mechanical; iv) The coefficient before the effective pure state densitymatrix, e, is a measure of the simultaneity of the molecules in an ensemble. It reflects the intensity of the NMR signaland has no significance in quantifying the entanglement in the bulk ensemble NMR system. The decomposition of thedensity matrix into product states is only an indication that the ensemble can be prepared by an ensemble with theparticles unentangled. We conclude that effective-pure-state NMR quantum computation is genuine, not just classicalsimulations.展开更多
Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are rev...Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_c<T_g^(PS-rich), the crystallization of thePEO blocks is observed to be confined within the bicontinuous D_(CF) phase due to the rapid vitrification of the PS-rich phase.Overall crystallization rate, crystal melting behavior, and crystallinity results further confirm the competition betweencrystallization and vitrification at different temperatures. In an ordered lamellar PEO-b-PS diblock copolymer, the crystalli-zation of the PEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the PS layers asobserved by time-resolved SAXS and WAXD experiments. From the combined two-dimensional SAXS and WAXDmeasurements, the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normalwhen it is isothermally crystallized at 35℃. In an ordered cylindrical PEO-b-PS sample, the crystallization of the PEO blocksis also observed to be confined within the ordered cylinders because of rapid vitrification of the PS matrix. The crystalorientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.展开更多
Formation of shish-kebab crystals using a bimodal polyethylene system containing high molecular weight(HMW)component with different ethyl branch contents was investigated.In situ small-angle X-ray scattering(SAXS)and ...Formation of shish-kebab crystals using a bimodal polyethylene system containing high molecular weight(HMW)component with different ethyl branch contents was investigated.In situ small-angle X-ray scattering(SAXS)and wide-angle X-ray diffraction(WAXD)techniques were used to monitor the formation and evolution of shish-kebab structure sheared at low temperature in simple shear mode and low rate.Only the bimodal PE with no branch formed shish-kebab crystals at the shear temperature of 129℃,and the shish length increased with the crystallization time,while bimodal PE with branch has no observable shish under the same conditions.The degree of crystallization for bimodal PE with no branch increased with time up to above 7%,while those with ethyl branch increased continually up to above 23%.Furthermore,bimodal PE's Hermans orientation factor with no branch increased to 0.60,while those with ethyl branch only increased to a value below 0.15.This study indicated that the shish-kebab crystal formed at the low temperature of 129℃is due to the stretch of entangled chains under shear for the bimodal PE with no branch.Only partly oriented lamellar crystals were formed for the bimodal PE with ethyl branch.All the results at the shear temperatures higher,closed to,and lower than the melting point,the modulation of shish crystals formation owing to different mechanisms of the coil-stretch transition and the stretched network by changing shear temperature was achieved in the bimodal PE samples.展开更多
The DNA heptamer [d(TCGCGCG)]_2,which has an alternating pyrimidine-purine se- quence and a dangling T residue at the 5′-end has been used as a model for studying conformational charac- teristics of DNA duplexes with...The DNA heptamer [d(TCGCGCG)]_2,which has an alternating pyrimidine-purine se- quence and a dangling T residue at the 5′-end has been used as a model for studying conformational charac- teristics of DNA duplexes with double-single strand junctions that occur during replication and transcription. The proton resonances of the molecule have been assigned by NOESY and TOCSY/HOHAHA experiments. The NOE intensities at seven different mixing times were quantified for calculating distance constraints with the two-spin approximation.The experiments have uncovered the interesting structural features of the molecule.The sugar proton coupling constants were determined by the P.E.COSY experiment for each residue of the duplex to examine the sugar conformations of the DNA heptamer.The structural features of the heptamer in solution have been obtained.The overall structure of the DNA duplex is basically of a B-type DNA,and substantial changes from a standard B-DNA have been observed,especially in the terminal region of the molecule.The dangling T residue was found in an unusual syn-conformation.展开更多
This study focuses on the behavior of chitosan(CHI)and its polyelectrolyte complexes with carboxymethyl starch(CMS)used as monolithic matrices with acetaminophen as drug tracer.Two different chitosan grades were teste...This study focuses on the behavior of chitosan(CHI)and its polyelectrolyte complexes with carboxymethyl starch(CMS)used as monolithic matrices with acetaminophen as drug tracer.Two different chitosan grades were tested alone or associated in various ratios with CMS as excipients for tablets obtained by direct compression.The degree of deacetylation(DDA)of CHI,estimated from 1H NMR and FTIR data,was correlated with X-ray diffraction and scanning electron microscopy(SEM)to evaluate structural organization of the monolithic matrices.In vitro drug dissolution assays showed major differences in CHI kinetic profiles between tablets exposed to acidic medium for 2h(to mimick gastric passage)prior to dissolution in simulated intestinal fluid(SIF),and those administered directly to SIF.Prior exposure to acidic SGF conducted to longer dissolution profiles(release completed after 16 h)and preservation of tablet shape,whereas tablets directly incubated in SIF were rapidly disintegrated.The improved properties of chitosan matrices exposed to SGF may be related to an outer compact coating layer(visible in SEM).The effect of self-stabilization of chitosan in acidic medium was compared to that due to formation of polyelectrolyte complexes(PEC)in co-processed polymeric systems(CHI:CMS).The self-formed membrane following exposure to gastric acidity appears to help maintaining tablet integrity and allows higher drug loading,recommending CHI and its complexes with CMS as excipients for drug delivery.展开更多
Based on the cosmological principle and quantum Yang-Mills gravity in the super-macroscopic limit, we obtain an exact recession velocity and cosmic redshift z, as measured in an inertial frame F≡F(t,x,y,z). For a mat...Based on the cosmological principle and quantum Yang-Mills gravity in the super-macroscopic limit, we obtain an exact recession velocity and cosmic redshift z, as measured in an inertial frame F≡F(t,x,y,z). For a matter-dominated universe, we have the effective cosmic metric tensor Gμν(t)=(B^2(t),-A^2(t),-A^2(t),-A^2(t)), A∝B∝t^1/2, where t has the operational meaning of time in F frame. We assume a cosmic action S≡Scos involving Gμν(t) and derive the ‘Okubo equation’ of motion, G^μν(t)■μS■νS-m^2=0, for a distant galaxy with mass m. This cosmic equation predicts an exact recession velocity, r=rH/[1/2+√1/4+r^2H^2/C0^2]<Co, where H=A(t)/A(t) and Co=B/A, as observed in the inertial frame F. For small velocities, we have the usual Hubble's law r≈rH for recession velocities. Following the formulation of the accelerated Wu-Doppler effect, we investigate cosmic redshifts z as measured in F. It is natural to assume the massless Okubo equation, G^μν(t)■μψe■νψe=0, for light emitted from accelerated distant galaxies. Based on the principle of limiting continuation of physical laws, we obtain a transformation for covariant wave 4-vectors between and inertial and an accelerated frame, and predict a relationship for the exact recession velocity and cosmic redshift, z=[(1+Vr)/(1-Vr^2)1/2]-1, where Vr=r/Co<1, as observed in the inertial frame F. These predictions of the cosmic model are consistent with experiments for small velocities and should be further tested.展开更多
Synthetic biology comprises engineering design principles to build biological and biomimetic devices with versatile applicability.This Special Issue is composed of contributions with roots in the 2019 and 2020 interna...Synthetic biology comprises engineering design principles to build biological and biomimetic devices with versatile applicability.This Special Issue is composed of contributions with roots in the 2019 and 2020 international Genetically Engineered Machine(iGEM)competitions,and present platforms that enable the implementation of SynBio to bio-medicine,bio-remediation,and bio-materials.The field of synthetic biology provides a vast and interdisciplinary engineering playground,where researchers harness a wide range of molecular building blocks and machinery to assemble devices that span from bio-engineered organisms displaying new and interesting functionalities[1]to synthetic-cell mimics able to coordinate bio-inspired behaviours[2].SynBio is thus a versatile and comprehensive toolkit for novel technologies with a unique potential for societal impact.展开更多
文摘Abstract Aim: To evaluate the antifertility effect ofAlstonia scholaris bark extract in male rats. Methods: In male Wistar rats Alstonia scholaris bark extract was given by oral route at a dose of 200 mg/day for 60 days. The fertility and testicular function were assessed by mating tests, sperm motility, sperm concentration, biochemical indices and testicular cell population dynamics. Results: Oral feeding with the extract at a dose of 200 mg/day for the period of 60 days did not cause body weight loss, while the weights of testes, epididymides, seminal vesicle and ventral prostate were significantly reduced. The production of step-19 spermatids was reduced by 79.6% in treated rats. The population of preleptotene and pachytene spermatocytes were decreased by 61.9% and 60.1%, respectively. Spermatogonia and Sertoli cell population were also affected. The seminiferous tubule and Leydig cell nuclear area were reduced significantly (P<0.01) when compared to the controls. Reduced sperm count and motility resulted in a total suppression of fertility. A significant fall in the protein and sialic acid content of the testes, epididymides, seminal vesicle and ventral prostate as well as glycogen content of testes were also noticed. The fructose content in the seminal vesicle was lowered whereas the testicular cholesterol was elevated as compared with the controls. The following compounds were obtained from the extract with chromatographic separation over Si-gel column: α-amyrin, β-amyrin, lupiol acetate, venenative, rhazine and yohimbine. Conclusion: At the dose level employed, Alstonia scholaris bark extract has a significant antifertility effect in male rats; the primary site of action may be post meiotic germ cells (Step 19 spermatids).
文摘A stability indicating LC method was developed for the simultaneous determination of Amlodipine and Benazepril capsules in pharmaceutical dosage form. Efficient chromatographic separation was achieved on Symmetry C18 stationary phase with simple combination of amobile phase containing 750 mL of DI Water, 250 mL of Acetonitrile and 2 mL of Octylamine into suitable container with adjusted pH to 2.50 ± 0.05 with the aid of Ortho phosphoric acid delivered in an isocratic mode and quantification was carried out using UV detection at 240 nm at a flow rate of 1.0 mL·min-1 with an injection volume of 20 μl and ambient column temperature. This method is capable to detect both the drug components of Amlodipine and Benazepril in presence of their degradation products (Amlodipine Imp-A and Benazepril Impurity-C) with a detection level of 0.05%. Amlodipine/Benazepril in their combination drug product were exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the samples were analysed. Peak homogeneity data of Amlodipine and Benazeprilis were obtained using PDA detector, in the stressed sample chromatograms, demonstrating the specificity. The method shows excellent linearity over a range of 0.05%-2.0% for Amlodipine, Amlodipine Impurity-A and 0.05%-5.0% for Benazepril and Benazepril Impurity-C. The correlation coefficient for Amlodipine and Benazepril is 1. The relative standard deviation was always less than 2%. The proposed method was found to be suitable and accurate for quantitative determination and the stability study of Amlodipine and Benazepril in pharmaceutical preparations. The developed HPLC method was validated with respect to linearity & range, accuracy, precision and robustness.
文摘 Transition metal-catalyzed decomposition of diazo compounds and subsequent transformations constitute vast synthetically useful reactions. Recently the catalytic approaches to ylide generation and reaction leading to heterocycle compounds from diazo compounds have achieved remarkable successes.……
文摘A new bimetallic complex containing Zn and La was prepared from a salen ligand possessing methoxyl groups at the 3, 3′-positions. The structural feature is that one of nitrate groups is disordered and displaced between two metal centers. Crystal system: Triclinic space group:P-1, Z=2. a=0.82714(17) nm, b=1.3484(3) (1) nm, and c=1 3898(3) (1) nm, α=79.89(3)°, β=76.67(3)°, and γ=72.43(3)°. V=1 428 6(5) nm3, Dx=1.812 g·cm-3. (Δρ)max=1 510×10-3 enm3, (Δρ)min=-1.503×10-3 enm3. Accordingly, two water molecules occupy the metal centers in the apical positions via the syn-geometry.
基金the Andrew Mellon Foundation,NSF Biocomplexity Program (Richter)NSF Career Grant BES-9984489(Vasudevan)and the EPA-STAR program (Fimmen) for funding.
文摘The objective of this study was to improve primary-amine nitrogen (1°-N) quantification in dissolved organic matter (DOM) originating from natural waters where inorganic forms of N, which may cause analytical interference, are commonly encountered. Efforts were targeted at elucidating organic-N structural criteria influencing the response of organic amines to known colorimetric and fluorescent reagents and exploring the use of divalent metal-assisted amide hydrolysis in combination with fluorescence analyse...
文摘 Peptide side-chain conformations, especially the aromatic side-chain residues, play an important role in the molecular recognition processes between peptide ligands and their corresponding receptors. The modifications on peptide side-chain can result in biological activity changes and many other property changes. β-alkyl constrained α- amino acids have been applied for peptide molecular design, and have resulted in some important results in peptideresearch in recent years.[1～3]……
文摘It has long been known that the configurational isomers of biologically active compounds, e.g., nutrients, pesticides, and drugs, may exhibit different activities in a chiral environment such as the human body. Although the majority of drugs presently in development are chiral, analytical and preparative methods for the quantitative determination and purification of stereoisomers still lag behind. One reason is that commonly used chiral selectors for the direct resolution of enantiomers are not tailor-made for a specific analyte. The identification of suitable selectors for a particular pair of enantiomers still requires considerable experimentation and is generally demanding with regard to material, time and labor. The rational design of chiral host molecules, therefore, represents a challenge in facilitating enantiomer analysis. In this article, we describe how a combination of techniques ranging from organic synthesis to molecular biology yields antibodies of predetermined specificity and stereoselectivity that can be used as tailor-made chiral selectors for the chromatographic separation of enantiomers and their sensitive detection in immunosensors.
基金This work has been supported in part by the Drexel & Hahnemann University Synergy Grant (YW & PIL)the Commonwealth of Pennsylvania through a grant to the Nanotechnology Institute of Southeastern Pennsylvania (YW, PIL & AGM),NIH (No. DE09848 to YW)US Army Research Office (YW) and NASA Graduate Student Research Fellowship (NAG9-1380)to P. Bidez. Y
文摘Conducting polymer, polyaniline （PANI）, has been studied as a novel electroactive and electrically conductive material for tissue engineering applications. The biocompatibility of the conductive polymer can be improved by （i） covalently grafting various adhesive peptides onto the surface of prefabricated conducting polymer films or into the polymer structures during the synthesis, （ii） co-electrospinning or blending with natural proteins to form conducting nanofibers or films, and （iii） preparing conducting polymers using biopolymers, such as collagen, as templates. In this paper, we mainly describe and review the approaches of covalently attaching oligopeptides to PANI and electrospinning PANI-gelatin blend nanofibers. The employment of such modified conducting polymers as substrates for enhanced cell attachment, proliferation and differentiation has been investigated with neuronal PC-12 cells and H9c2 cardiac myoblasts. For the electrospun PANI- gelatin fibers, depending on the concentrations of PANI, H9c2 cells initially displayed different morphologies on the fibrous substrates, but after one week all cultures reached confluence of similar densities and morphologies. Furthermore, we observed, that conductive PANI, when maintained in an aqueous physiologic environment, retained a significant level of electrical conductivity for at least 100 h, even though this conductivity was decreasing over time. Preliminary data show that the application of micro-current stimulates the differentiation of PC-12 cells. All the results demonstrate the potential for using PANI as an electroactive polymer in the culture of excitable cells and open the possibility of using this material as an electroactive scaffold for cardiac and/or neuronal tissue engineering applications that require biocompatibility of conductive polymers.
基金Supported by the National Natural Science Foundation of China
文摘Pyrrololactam type of alkaloids was found in many marine sponges which belong to the family Axinellidae. In the course of our systematic research for bioactive substances in marine organisms, we studied the sponge Phacellia fusca Schmidt which also belongs to the family Axinelldae. From the chloroform-soluble fraction, ten A-nor-sterols were isolated and identified, while from the water-soluble portion, three known pyrrololactam alkaloids and a new pyrrololactam alkaloid, which was named fuscin, were obtained. The present paper contains the isolation and structure determination of fuscin (1).
文摘A wide variety of different types of microorganisms are known to produce intracellular energy and carbon storage products, which have been generally described as being poly (β-hydroxybutyrate), PHB, but which are, more often than not, copolymers containing different alkyl groups at the β-position. Hence, PHB belongs to the family ofpoly (β-hydroxyalkanoastes), PHA, all of which are usually formed as intracellular inclusions in bacteria under unbalanced growth conditions. Recently, it became of industrial interest to evaluate these PHA polyesters as natural biodegradable and biocompatible plastics for a wide range of possible applications, such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such 'tailor-made' copolymers can be produced under controlled growth conditions in that, if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.
基金The project supported by National Fundamental Research Program under Grant No. 001CB309308, and National Natural Science Foundation of China under Grant No. 60073009, the Hang Tian Science Fund, and the Excellent Young University Teachers' Fund of the Education Ministry of Chnia
文摘The quantum nature of bulk ensemble NMR quantum computing the center of recent heated debate,is addressed. Concepts of the mixed state and entanglement are examined, and the data in a two-qubit liquid NMRquantum computation are analyzed. The main points in this paper are: i) Density matrix describes the "state" of anaverage particle in an ensemble. It does not describe the state of an individual particle in an ensemble; ii) Entanglementis a property of the wave function of a microscopic particle (such as a molecule in a liquid NMR sample), and separabilityof the density matrix cannot be used to measure the entanglement of mixed ensemble; iii) The state evolution in bulk-ensemble NMRquantum computation is quantum-mechanical; iv) The coefficient before the effective pure state densitymatrix, e, is a measure of the simultaneity of the molecules in an ensemble. It reflects the intensity of the NMR signaland has no significance in quantifying the entanglement in the bulk ensemble NMR system. The decomposition of thedensity matrix into product states is only an indication that the ensemble can be prepared by an ensemble with theparticles unentangled. We conclude that effective-pure-state NMR quantum computation is genuine, not just classicalsimulations.
文摘Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_c<T_g^(PS-rich), the crystallization of thePEO blocks is observed to be confined within the bicontinuous D_(CF) phase due to the rapid vitrification of the PS-rich phase.Overall crystallization rate, crystal melting behavior, and crystallinity results further confirm the competition betweencrystallization and vitrification at different temperatures. In an ordered lamellar PEO-b-PS diblock copolymer, the crystalli-zation of the PEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the PS layers asobserved by time-resolved SAXS and WAXD experiments. From the combined two-dimensional SAXS and WAXDmeasurements, the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normalwhen it is isothermally crystallized at 35℃. In an ordered cylindrical PEO-b-PS sample, the crystallization of the PEO blocksis also observed to be confined within the ordered cylinders because of rapid vitrification of the PS matrix. The crystalorientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.
基金the National Natural Science Foundation of China(Nos.51773101 and 51973097).
文摘Formation of shish-kebab crystals using a bimodal polyethylene system containing high molecular weight(HMW)component with different ethyl branch contents was investigated.In situ small-angle X-ray scattering(SAXS)and wide-angle X-ray diffraction(WAXD)techniques were used to monitor the formation and evolution of shish-kebab structure sheared at low temperature in simple shear mode and low rate.Only the bimodal PE with no branch formed shish-kebab crystals at the shear temperature of 129℃,and the shish length increased with the crystallization time,while bimodal PE with branch has no observable shish under the same conditions.The degree of crystallization for bimodal PE with no branch increased with time up to above 7%,while those with ethyl branch increased continually up to above 23%.Furthermore,bimodal PE's Hermans orientation factor with no branch increased to 0.60,while those with ethyl branch only increased to a value below 0.15.This study indicated that the shish-kebab crystal formed at the low temperature of 129℃is due to the stretch of entangled chains under shear for the bimodal PE with no branch.Only partly oriented lamellar crystals were formed for the bimodal PE with ethyl branch.All the results at the shear temperatures higher,closed to,and lower than the melting point,the modulation of shish crystals formation owing to different mechanisms of the coil-stretch transition and the stretched network by changing shear temperature was achieved in the bimodal PE samples.
文摘The DNA heptamer [d(TCGCGCG)]_2,which has an alternating pyrimidine-purine se- quence and a dangling T residue at the 5′-end has been used as a model for studying conformational charac- teristics of DNA duplexes with double-single strand junctions that occur during replication and transcription. The proton resonances of the molecule have been assigned by NOESY and TOCSY/HOHAHA experiments. The NOE intensities at seven different mixing times were quantified for calculating distance constraints with the two-spin approximation.The experiments have uncovered the interesting structural features of the molecule.The sugar proton coupling constants were determined by the P.E.COSY experiment for each residue of the duplex to examine the sugar conformations of the DNA heptamer.The structural features of the heptamer in solution have been obtained.The overall structure of the DNA duplex is basically of a B-type DNA,and substantial changes from a standard B-DNA have been observed,especially in the terminal region of the molecule.The dangling T residue was found in an unusual syn-conformation.
文摘This study focuses on the behavior of chitosan(CHI)and its polyelectrolyte complexes with carboxymethyl starch(CMS)used as monolithic matrices with acetaminophen as drug tracer.Two different chitosan grades were tested alone or associated in various ratios with CMS as excipients for tablets obtained by direct compression.The degree of deacetylation(DDA)of CHI,estimated from 1H NMR and FTIR data,was correlated with X-ray diffraction and scanning electron microscopy(SEM)to evaluate structural organization of the monolithic matrices.In vitro drug dissolution assays showed major differences in CHI kinetic profiles between tablets exposed to acidic medium for 2h(to mimick gastric passage)prior to dissolution in simulated intestinal fluid(SIF),and those administered directly to SIF.Prior exposure to acidic SGF conducted to longer dissolution profiles(release completed after 16 h)and preservation of tablet shape,whereas tablets directly incubated in SIF were rapidly disintegrated.The improved properties of chitosan matrices exposed to SGF may be related to an outer compact coating layer(visible in SEM).The effect of self-stabilization of chitosan in acidic medium was compared to that due to formation of polyelectrolyte complexes(PEC)in co-processed polymeric systems(CHI:CMS).The self-formed membrane following exposure to gastric acidity appears to help maintaining tablet integrity and allows higher drug loading,recommending CHI and its complexes with CMS as excipients for drug delivery.
基金Supported in part by Jing Shin Research FundProf.Leung Memorial Fund of the UMassD Foundation
文摘Based on the cosmological principle and quantum Yang-Mills gravity in the super-macroscopic limit, we obtain an exact recession velocity and cosmic redshift z, as measured in an inertial frame F≡F(t,x,y,z). For a matter-dominated universe, we have the effective cosmic metric tensor Gμν(t)=(B^2(t),-A^2(t),-A^2(t),-A^2(t)), A∝B∝t^1/2, where t has the operational meaning of time in F frame. We assume a cosmic action S≡Scos involving Gμν(t) and derive the ‘Okubo equation’ of motion, G^μν(t)■μS■νS-m^2=0, for a distant galaxy with mass m. This cosmic equation predicts an exact recession velocity, r=rH/[1/2+√1/4+r^2H^2/C0^2]<Co, where H=A(t)/A(t) and Co=B/A, as observed in the inertial frame F. For small velocities, we have the usual Hubble's law r≈rH for recession velocities. Following the formulation of the accelerated Wu-Doppler effect, we investigate cosmic redshifts z as measured in F. It is natural to assume the massless Okubo equation, G^μν(t)■μψe■νψe=0, for light emitted from accelerated distant galaxies. Based on the principle of limiting continuation of physical laws, we obtain a transformation for covariant wave 4-vectors between and inertial and an accelerated frame, and predict a relationship for the exact recession velocity and cosmic redshift, z=[(1+Vr)/(1-Vr^2)1/2]-1, where Vr=r/Co<1, as observed in the inertial frame F. These predictions of the cosmic model are consistent with experiments for small velocities and should be further tested.
文摘Synthetic biology comprises engineering design principles to build biological and biomimetic devices with versatile applicability.This Special Issue is composed of contributions with roots in the 2019 and 2020 international Genetically Engineered Machine(iGEM)competitions,and present platforms that enable the implementation of SynBio to bio-medicine,bio-remediation,and bio-materials.The field of synthetic biology provides a vast and interdisciplinary engineering playground,where researchers harness a wide range of molecular building blocks and machinery to assemble devices that span from bio-engineered organisms displaying new and interesting functionalities[1]to synthetic-cell mimics able to coordinate bio-inspired behaviours[2].SynBio is thus a versatile and comprehensive toolkit for novel technologies with a unique potential for societal impact.
