Acceleration of carbon-13 spin-lattice relaxation times in amino acids by electrolytes

A series of amino acids and carboxylic acids were determined by C NMR spectroscopy. 13 The results showed that addition of 3M MgCl2 led to the C NMR integral area of samples being 13 well proportional to number of carbon atoms that produce the particular signal with reliability over 95%. Measurements of C spin-lattice relaxation times (T1’s) are reported for a number of amino 13 acids. T1’s of all the carbons in amino acids generally tend to decrease with the increase of the c…     

Helical secondary structures and supramolecular tilted chirality in N-terminal aryl amino acids with diversified optical activities

Helix structures at atomic/molecular level have not been found in self-assembled peptide seque nce with less than three residues.As β-sheet supramolecular secondary structures have been discovered in solidstate amino acids,we here report the conjugation of simple N-terminal aryl protecting group could give rise to helical supramolecular secondary structures in solid-state,which determines the optical activities of the adjacent aryl groups.The carboxylic acid-involved asymmetric H-bonds in N-te rminal aryl amino acids induce the emergence of super-helical structures of amino acid residues and aryl groups.In most cases,supramolecular tilted chirality of aryl groups is opposite to that of amino acid sequences,of which handedness and helical pitch are determined by the H-bond modalities.Determining correlation between supramolecular tilted chirality of aryl segments and their chiroptical activities is firstly unveiled,which was verified by the computational results based on density functional theory.Most aryl amino acids self-assembled by nanoprecipitation method via crystallization induced self-assembly into rigid one-dimensional microstructures with ultra-high Young's modulus.This study reveals the generic existence of chiral supramolecular structure s in aggregated amino acid derivatives and gives an in-depth investigation into the structural-property relationships,which could guide the rational design and screening of chiroptical supramolecular materials.     

Interaction of antigen and antibody on core-shell polymeric microspheres

Monodispersed microspheres with polystyrene as the core and poly(acrylamide-co-N-acryloxysuccinirnide) as the shell were synthesized by a two-step surfactant-free emulsion copolymerization.The core-shell morphology of the microspheres was shown by scanning electron microscopy and transmission electron microscopy.Rabbit immunoglobulin G (as antigen) was covalently coupled onto the microspheres by the reaction between succinimide-activated ester groups on the shell of the microspheres and amino groups of the antigen molecules.The size of particles was characterized by dynamic light scattering technique and was found to vary upon bioconjugation and interaction with proteins.The binding process was shown to be specific to goat anti-rabbit immunoglobulin G(as antibody) and reversible upon the addition of free antigen into the system.     

不同温度下α-氨基酸在CTAB溶液中的体积及折光率的变化

Densities(ρ)and refractive indices(nD)of glycine(Gly),DL-alanine(Ala),DL-valine(Val)(0.02,0.04,0.06,0.08,and 0.10 mol·L-1)in 0.005 and 0.008 mol·L-1 aqueous cetyltrimethylammonium bromide(CTAB)have been measured at 298.15,303.15,308.15,and 313.15 K.The density data have been utilized to calculate apparent molar volumes(φv),partial molar volumes(φ0v),at infinite dilution and partial molar volumes of transfer φ0v(tr)of amino acids.The refractive index data have been used to calculate molar refractivity(RD)of amino acids in aqueous cetyltrimethylammonium bromide.It has been observed that φ0v varies linearly with increasing number of carbon atoms in the alkyl chain of amino acids,and hence,was split to get contributions from the zwitterionic end groups(NH 3,COO-)and methylene group(CH2)of the amino acids.The behaviour of these parameters has been used to investigate the solute-solute,solute-solvent interactions and the effect of cetyltrimethylammonium cation on these interactions.     

Theoretical Studies on Complexes of Calcium Ion with Amino Acids

The complexes formed by calcium ion and 12 common amino acids were investigated systematically in the gas phase at the level of MP2/6-311＋＋G（d,p）//MP2/6-3 1G（d,p）.The results show that the salt-bridge structure is the most preferred motif for Ca2＋ binding aliphatic amino acids without heteroatom in the side chain,while charge-solvated（CS） structure is the most preferred motif for Ca2＋ binding other amino acids except for glutamine and lysine.IR spectra of Gln-Ca2＋ and Asn-Ca2＋ complexes were calculated and compared well with the available experiments.From the study in aqueous solution,the bidentate salt-bridge structure was determined to be the most favorable for all the twenty kinds of amino acids to chelate Ca2＋ to both the oxygen atoms of the negatively carboxylate group in the backbone.     

Multiresponsive Polymer Assemblies Achieved by a Subtle Chain Terminal Modification

Inspired by the influence of chemical structure of end groups on the phase transition temperature of thermoresponsive polymers,we demonstrated a strategy to control the multi-responsiveness of polymer assemblies via subtle modification of end groups of thermoresponsive polymer segments and revealed its potential application for drug delivery.By developing polymer assemblies composed of poly(aliphatic ester) as the inner core and thermoresponsive polyphosphoester as the outer shell,we showed that end groups of thermoresponsive polyphosphoester segments controlled the surface property of assemblies and further determined the stimuli-responsive behavior.The phase-transition temperatures of the unmodified polymer assemblies are tightly controlled by their surface properties due to the hydrophilic to hydrophobic transitions of end groups in response to an environmental stimulus (e.g.pH or light irradiation).External control over these surface properties can by asserted by adjusting the chemical structure and composition of the terminal groups of the thermoresponsive polyphosphoesters.     

The amphiphilic multiarm copolymers based on hyperbranched polyester and lysine: Synthesis and self-assembly

The amphiphilic multiarm copolymers were synthesized through the modification of commercially available hyperbranched polyesters(Boltorn H40) with N-ε-carbobenzoxy-L-Lysine N-carboxyanhydride(ZLys-NCA).After being condensed with N-Boc-phenylalanine(Boc-~NPhe) and deprotected the Boc-groups in trifluoroacetic acid(TFA),the original terminal hydroxyl groups were transformed into the amino groups and then initiated the ring-opening polymerization of ZLys-NCA.The hydrophilic poly(L-lysine) was grafted to the surface of Boltorn H40 successfully after the protecting benzyl groups were removed by the HBr solution in glacial acetic acid(33 wt%).The resulting multiarm copolymers were characterized by the ~1H-NMR,GPC and FTIR.The arm length calculated by NMR and GPC analysis was about 3 and 13 lysine-units for H40-Phe-PLysl and H40-Phe-PLys2 respectively.Due to the amphiphilic molecular structure,they displayed ability to self-assemble into spherical micelles in aqueous solution with the average diameter in the range from 70 nm to 250 nm.The CMC of H40-Phe-PLysl and H40-Phe-PLys2 was 0.013 mg/mL and 0.028 mg/mL,respectively, indicating that H40-Phe-PLysl with shorter arm length is easier to self-assemble than H40-Phe-PLys2 with longer arm length.     

DOPA-IGF-1 Coated HA/PLGA Microspheres Promoting Proliferation and Osteoclastic Differentiation of Rabbit Bone Mesenchymal Stem Cells

To explore the ability of dihydroxyphenylalanine-insulin-like growth factor-1 (DOPA-IGF-1) coated hydroxyapatite/poly(lactic-co-glycolic acid)(HA/PLGA) microspheres to promote the proliferation and osteoclastic differentiation of rabbit bone mesenchymal stem cells(rBMSCs), HA/PLGA microspheres with different HA content (10%, 30%, 50%, mass fraction) were prepared by electrospinning method and HA/PLGA microspheres with 50% HA were coated with IGF-1 and DOPA-IGF-1, respectively. They were co-cultured with rBMSCs, respctively. Cell counting kit-8(CCK-8) detection, confocal laser scanning microscopy(CLSM), alkaline phosphatase(ALP) detection and osteogenesis related genes COL IA1, Runx2 and bone morphogenetic protein-2(BMP-2) detection were conducted to detect the proliferation activity, cell morphology, differentiation ability and the expression level of osteogenesis-related genes of cells cultured on all microspheres groups. The results showed that rBMSCs proliferation increased in an HA content dependent manner, and cells proliferated more in the IGF-1 coated and DOPA-IGF-1 coated groups, in particular in DOPA-IGF-1 coated group, and the differences were more remarkable over time (P<0.05). HA/PLGA microspheres promoted the proliferation and osteogenic differentiation of rBMSCs, and DOPA-IGF-1 coating enhanced the proliferation and osteogenic differentiation of rBMSCs.     

Recent progress of sugar amino acids: Synthetic strategies and applications as glycomimetics and peptidomimetics

In order to meet the increasing demands for the development of large varieties of new molecules for discovering new drugs and materials, organic chemists are developing many novel multifunctional building blocks, which are assembled rationally to create ‘nature-like' and yet unnatural organic molecules with well-defined structures and useful properties. Sugar amino acids(SAAs), the carbohydrate derivatives bearing both amino and carboxylic acid functional groups, are important ones of these multifunctional building blocks, which can be used to create novel materials with potential applications as glycomimetics and peptidomimetics. This review will focus on recent synthetic strategies of SAAs and their applications in creating large number of structurally diverse glycomimetics and peptidomimetics.     

A Thermochemical Study of the Reaction of Lanthanum Nitrate with Alanine

IntroductionRare earth ions possess some special functions, in biochemistry and can be used as aprobe to label the calcium ion, moreover, amino acids are the structure unit of proteins, so itis very important to make research on the complexes of rare earth salts with amino acids. Theresearch on the behaviour of the complexes of rare earth salts with amino acids has become aheated point of the research in the crossing field of chemistry and biology in recent years['--'].In order to guide the de…     

THE EFFECT OF IONIC STRENGTH ON THE UPTAKE OF TAURINE ON A STRONG-BASIC ANION EXCHANGE RESIN

1. INTRODUCTION Taurine (NH2CH2CH2SO3H) is one of the most important amino acids in the human body, and plays an important role in a variety of physiological functions, pharmacological actions and pathological conditions, such as in controlling epilepsy, hypertension and arrhythmia. It is also often used to recover osmotic pressure and promote cerebrum growth [1,2]. As one of amino acids, taurine had the amphoteric characteristic which can be utilized in the ion-exchange technique to e…     

EXPRESSION OF A PARTIAL SYNTHETIC HUMAN TNF cDNA IN E. coli

A recombinant human tumour necrosis factor (rhTNF) cDNA was constructed. The TNF gene was isolated from a human genomic gene library. There are four exons in the TNF gene. The fourth exou codes for 140 amino acids of the TNF matured protein which is composed of 157 amino acids. A major portion of the fourth exon was isolated and then ligated to a synthesized DNA fragment coding for the remaining amino acids. The partial synthetic hTNF (rhTNF) cDNA thus generated was subcloned into a vector and successfully expressed in E. coli. 5-1 fer1entator was used to produce rhTNF. About 20g (wet weight) of bacterial pellet per liter medium and 106—10~7 units of cytotoxicity to L929 cells per milliliter medium were obtained. rhTNF was purified by HPLC and dried with a freeze dryer, rhTNF with a purity of about 95% in the form of white powder was obtained. The sequence of ten amino acids at the amino terminus of the rhTNF was determined. The result showed that it was identical with that of the natural human TNF.     

Synthesis of monodisperse hollow polymer microspheres with functional groups by distillation precipitation polymerization

<正>Monodisperse hollow polymer microspheres having various functional groups on the shell-layer,such as carboxylic acid,pyridyl and amide,were prepared by two-stage distillation precipitation polymerization in neat acetonitrile in the absence of any stabilizer or additive,during which monodisperse poly(methacrylic acid)(PMAA) afforded from the first-stage polymerization was utilized as the seeds for the second-stage polymerization.The shell layer with different functional groups was formed during the second-stage copolymerization of either divinylbenzene(DVB) or ethyleneglycol dimethacrylate(EGDMA) as crosslinker and the functional comonomers,in which the hydrogen-bonding interaction between the carboxylic acid group of PMAA core and the functional groups of the corresponding comonomers,including carboxylic acid,amide and pyridyl,played an essential role for the formation of monodisperse core-shell functional microspheres.The hollow polymer microspheres were then developed after the subsequent removal of PMAA cores by dissolution in ethanol under basic condition.Transmission electron microscopy(TEM) and scanning electron microscopy (SEM) were used to determine the morphology of the resultant PMAA core,functional core-shell microspheres and the corresponding hollow polymer microspheres with different functional groups.FT-IR spectra confirmed the successful incorporation of the various functional groups on the shell layer of the hollow polymer microspheres.     

Micellar Copolymerization: the State of the Arts

Over the past two decades, hydrophobically modified water-soluble polymers (HMWSPs), particularly hydrophobically associating polyacrylamides (HAPAMs), have attracted increased interest owing to their practical and fundamental importance[1]. This system usually consists of a hydrophilic backbone with a small proportion (generally less than 2 mol %) of hydrophobic pendent groups. When dissolved in aqueous solutions, the apolar moieties tend to exclude water and are held together by intra- a…     

STRUCTURE OF THE MITOCHONDRIAL URFA6L GENE AND tRNA~(Lys) GENE FROM CARP

The carp mitochondrial URFA6L gene consists of 165 base pairs. The overall structural organization of the gene is very similar to that of the Xenopus URFA6L gene. Their nucleotide sequences exhibit 68% homology. The carp URFA6L gene encodes a protein of 54 amino acids. The amino acid composition of the protein is unusual because almost half of the residues consist of 5 hydrophobic amino acids(proline, tryptophan, leueine, isoleueine and tyrosine). A comparison between the amino acid sequences of 5 vertebrate URFA6L proteins and the yeast ATPase8 showed that they have weak but very important common structural features, suggesting that the vertebrate URFA6L proteins may function asATPase8. The nucleotide sequence of the lysine tRNA gene from carp has been determined and represented in cloverleaf secondary structure. Similar to amphibian and mammalian mitochondrial tRNA~(Lys) genes, the carp mitochondrial tRNA~(Tys) gene also has some unusual structural features as compared with its cytoplasmic counterpart     

HORMONAL REGULATION OF CALLUS FORMATION IN RELATION TO NUCLEIC ACIDS AND AMINO ACIDS METABOLISM

The cotyledon segments of mung bean were cultured On Miller's medium with or without auxins and cytokinins. It was found that NAA and kinetiu were both required for callus formation and the growth rate increased proportionally to their concentrations. RNA and protein synthesis increased in the early stage of callus formation and the increase of the total RNA was mainly due to the increase of 25S and 18S RNA. In addition, it has been shown that the total amount of free amino acids in the control segments obviously increased after incubation and was larger than that in the callus-forming segments. On the other hand, the amount of protein amino acids in the callus-forming segments was larger than that in the control. Both proline and hydroxyproline existed in the control and callus-forming segments were increased, but the ratio of hydroxyprolinc and proline in the callus-forming segments was tfigher than that in the control.     

Prevalent intrinsic emission from nonaromatic amino acids and poly(amino acids)

Nonaromatic amino acids are generally believed to be nonemissive, owing to their lack of apparently remarkable conjugation within individual molecules. Here we report the intrinsic visible emission of nonaromatic amino acids and poly(amino acids) in concentrated solutions and solid powders. This unique and widespread luminescent characteristic can be well rationalized by the clustering-triggered emission(CTE) mechanism, namely the clustering of nonconventional chromophores(i.e. amino, carbonyl,and hydroxyl) and subsequent electron cloud overlap with simultaneous conformation rigidification. Such CTE mechanism is further supported by the single crystal structure analysis, from which 3 D through space electronic communications are uncovered.Besides prompt fluorescence, room temperature phosphorescence(RTP) is also detected from the solids. Moreover, persistent RTP is observed in the powders of exampled poly(amino acids) of ε-poly-L-lysine(.-PLL) after ceasing UV irradiation. These results not only illustrate the feasibility of employing the building blocks of nonaromatic amino acids in the exploration of new luminescent biomolecules, but also provide significant implications for the emissions of peptides and proteins at aggregated or crystalline states. Meanwhile, they may also shed lights on further understanding of autofluorescence from biological systems.     

Synthesis of Micron-size Functional Polystyrene Fluorescent Microspheres and their Adsorbability to Human Serum Albumin

Polystyrene microspheres with sulfo- or aldehyde- surface were synthesized through dispersion polymerization. Functional polystyrene fluorescent microspheres were prepared by the way of adding 2, 5-diphenyloxazole (PPO) into the reaction system directly and dying the blank microspheres in the ethanol solution of PPO. The influence of preparing matters on the encapsulating rate of PPO, and the influence of functional groups on the adsorbability to human serum albumin (HSA) were investigated.     

High-performance anion-exchange chromatography of carbohydrates using a new resin and pulsed amperometric detection

Summary This paper reports the results of a study on the use of a new polymer-based, strong anion-exchange, stationary phase for rapid and selective separation of carbohydrates and related compounds by high-pH, anion-exchange chromatography with pulsed amperometric detection. The new adsorbent has been obtained by direct nitration of 2.8 μm, spherical non-porous highly cross-linked, styrene-divinylbenzene copolymer beads, followed by reduction of superficially introduced nitro groups with nascent hydrogen and quaternization of the resultant amino groups with iodomethane. It is reported that by optimizing the ionic strength of the mobile phase, columns packed with the new anion-exchanger can be successfully employed to separate, either in isocratic or gradient elution mode, oligosaccharides, positional isomers of gluco-disaccharides, as well as uronic acids and sugar monophosphates.     

Preparation of Porous Polylactide Microspheres and Their Application in Tissue Engineering

In this study,porous polylactide (PLA) microspheres with different structures were prepared through the multiple emulsion solvent evaporation method.By changing organic solvents (ethyl acetate and chloroform) and adding effervescent salt NH4HCO3 in the inner water phase,microspheres with porous capsular,matrix,microcapsular and multivesicular structures were prepared.The protein encapsulation and release,and the cell growth behavior of porous microspheres were further explored.Under the same inner water phase,microspheres prepared with chloroform had higher protein encapsulation efficiency and less protein release rate as compared with those prepared with ethyl acetate.Cell experiments showed that the relatively rough surface of microspheres prepared with chloroform was more favorable for the cell growth in comparison with the smooth surface of microspheres prepared with ethyl acetate.This study shows a simple and effective method to control the protein release and cell growth behaviors of polymer microspheres by tuning their porous structure.