The purification and properties of the aspartate aminotransferase and aromatic-amino-acid aminotransferase from Escherichia coli.

A simple and convenient procedure is described for the isolation in good yield of two amino-transferases from various strains of Escherichia coli. On the basis of their substrate specificities one of the enzymes has been classified as an aromatic amino acid aminotransferase and the other as an aspartate aminotransferase, but both act on a wide range of substrates. Pyridoxal phosphate is bound more strongly to the aspartate aminotransferase than to the aromatic amino transferase which cannot be fully re-activated after removal of the prosthetic group. Both enzymes are composed of two subunits which appear to be identical.     

Solution-phase secondary-ion mass spectrometry of protonated amino acids

Although sulfolane proved unexpectedly to be a poor solvent for solution-phase secondary-ion mass spectrometry of underivatized amino acids in the presence of thallium(I) salts, glycerol was somewhat more effective. Also, the addition of trifluoromethanesulfonic acid proved more effective than addition of the metal in generating molecular ion complexes. A convenient and reliable method for rapidly determining amino acid molecular ions is based on these observations.     

An o-phthalaldehyde spectrophotometric assay for proteinases

A rapid and convenient spectrophotometric assay has been devised to measure proteolysis. The assay is based on the reaction of o-phthalaldehyde (OPA) and 2-mercaptoethanol with amino groups released during proteolysis of a protein substrate. The reaction is specific for primary amines in amino acids, peptides, and proteins, approaches completion within 1 to 2 min at 25 degrees C (half-times of approx 10-15 s), and requires no preliminary heating or separation of the hydrolyzed products from the undegraded protein substrate prior to performing the assay. The OPA assay was relatively as successful as a 2,4,6-trinitrobenzenesulfonic acid (TNBS) procedure in predicting the extent of hydrolysis of a protein substrate. The utility of the OPA method was demonstrated by measuring the degree of proteolytic degradation caused by trypsin, subtilisin, Pronase, and chymotrypsin of various soluble protein substrates. Ethanethiol (instead of 2-mercaptoethanol) or 50% of dimethyl sulfoxide can be included in the assay solution to stabilize certain OPA-amine products. The present method approaches the sensitivity of ninhydrin and TNBS procedures, is more convenient and rapid, and could substitute for these reagents in most assay systems.     

Synthesis of camptothecin–amino acid carbamate linkers

A more convenient and facile approach for the synthesis and production of camptothecin–amino acids carbamate linkers, that can be used in the synthesis of bioconjugate peptides JF-10-81, JF-10-71, and other peptide analogs designed to target somatostatin receptors has been described.     

化学比色法测定发酵液中L-缬氨酸的研究

应用“化学比色法”对发酵液中L -缬氨酸进行了定量分析研究 ,确立了L -缬氨酸定量测定条件和计算方法。以高速氨基酸分析仪测定结果为参比 ,用化学比色法测定结果的准确度比纸层析 -色斑洗脱比色法高 ,且应用化学比色法测定L-缬氨酸的含量较为方便。     

Synthesis of nucleotide oligomer having amino group in the side chain of internucleotidic bond

A convenient synthesis of d(TpT) derivative having amino group in the side chain of internucleotidic bond was achieved in a high yield using dichlorophosphoramidite as a phosphorylating reagent.     

Nonatomic solvent-driven Voronoi tessellation of proteins: an open tool to analyze protein folds

A three-dimensional Voronoi tessellation of folded proteins is used to analyze geometrical and topological properties of a set of proteins. To each amino acid is associated a central point surrounded by a Voronoi cell. Voronoi cells describe the packing of the amino acids. Special attention is given to reproduction of the protein surface. Once the Voronoi cells are built, a lot of tools from geometrical analysis can be applied to investigate the protein structure; volume of cells, number of faces per cell, and number of sides per face are the usual signatures of the protein structure. A distinct difference between faces related to primary, secondary, and tertiary structures has been observed. Faces threaded by the main-chain have on average more than six edges, whereas those related to helical packing of the amino acid chain have less than five edges. The faces on the protein surface have on average five edges within 1% error. The average number of faces on the protein surface for a given type of amino acid brings a new point of view in the characterization of the exposition to the solvent and the classification of amino acid as hydrophilic or hydrophobic. It may be a convenient tool for model validation.     

De novo peptide sequencing using ion peak intensity and amino acid cleavage intensity ratio

MOTIVATION: Peptide-sequencing methods by mass spectrum use the following two approaches: database searching and de novo sequencing. The database-searching approach is convenient; however, in cases wherein the corresponding sequences are not included in the databases, the exact identification is difficult. On the other hand, in the case of de novo sequencing, no preliminary information is necessary; however, continuous amino acid sequence peaks and the differentiation of these peaks are required. It is, however, very difficult to obtain and differentiate the peaks of all amino acids by using an actual spectrum. We propose a novel de novo sequencing approach using not only mass-to-charge ratio but also ion peak intensity and amino acid cleavage intensity ratio (CIR). RESULTS: Our method compensates for any undetectable amino acid peak intervals by estimating the amino acid set and the probability of peak expression based on amino acid CIR. It provides more accurate identification of sequences than the existing methods, by which it is usually difficult to sequence.     

Efficient synthesis of oligonucleotide conjugates on solid-support using an (aminoethoxycarbonyl)aminohexyl group for 5′-terminal modification

Solid-support conjugation at the 5′-terminal primary amine of oligonucleotides is a convenient and powerful method for introducing various functional groups. However, conventional aliphatic amines do not necessarily provide conjugates with sufficient yields. To improve the modification efficacy, we used the amino-linker (aminoethoxycarbonyl)aminohexyl group (ssH-linker), for solid-support conjugation. In the ssH-linker terminal modification, reactive free amino group could be easily presented onto a solid-support due to rapid removal of the amino-protecting group, and activated amino acids or cholesterol molecules could be covalently connected more efficiently than to typical 6-aminohexyl-linkers. Based on these results, the ssH-linker can be a useful terminal modification for the solid-support conjugation of functional molecules.     

嗜盐古生菌AJ4中BR蛋白基因部分片段和16S rRNA基因序列研究

为了研究分析新疆阿尔金山国家自然保护区阿牙克库木湖嗜盐古生菌物种与细菌视紫红质(bacteriorhodopsin ,BR)蛋白资源 ,对分离纯化到的极端嗜盐古生菌AJ4 ,采用PCR方法扩增出其 16SrRNA基因 (16SrDNA)和编码螺旋C至螺旋G的BR蛋白基因片断 ,并测定了基因的核苷酸序列 .通过BR蛋白部分片段序列分析表明 ,BR蛋白中对于完成质子泵功能以及与视黄醛结合的关键性氨基酸残基均为保守序列 ,位于膜内侧的序列比位于膜外侧的序列更保守 ;基于BR蛋白基因和16SrDNA序列的同源性比较以及 16SrDNA序列的系统发育学研究表明 ,AJ4是Haloarcula属中新成员 .由此建立了一种快速筛选具有新BR蛋白的新嗜盐古生菌的方法 .     

The use of optical emission spectroscopy for human 15N tracer studies.

Optical emission spectroscopy is a convenient method for determing ¹⁵N specific activity in a variety of metabolites following the administration of an ¹⁵N-labeled amino acid to humans. The only disadvantage, compared to the more conventional isotope ratio mass spectrometer analytical system is that more tracer is needed to give accurate results. When an ¹⁵N-labeled amino acid is used as the ¹⁵N carrier, the amount of ¹⁵N is not above a tracer dose. A suitable procedure is described for performing such studies using [¹⁵N]glycine as a tracer. As an experimental example, [¹⁵N]glycine was infused into a subject at a rate of 35 mg of N/hr for 8 hr. After 3 hr a meal was consumed by the subject. The urinary urea-¹⁵N, ammonia-¹⁵N and amino acid-¹⁵N profiles were determined.     

A biomimetic domino reaction for the concise synthesis of capreomycidine and epicapreomycidine

The non-proteinogenic amino acids capreomycidine and epicapreomycidine are constituents of antibiotically active natural products, but the synthesis of these unusual cyclic guanidine derivatives is challenging. The biosynthesis of capreomycidine has therefore been employed as a guideline to develop a concise biomimetic synthesis of both epimeric amino acids. The resulting domino-guanidinylation-aza-Michael-addition reaction provides the most convenient access to these amino acids in racemic form. Attempts to dissect the domino reaction into two separate transformations for a stereocontrolled version of this synthetic approach have also been made. The synthesized didehydro-arginine derivatives with urethane-protected guanidine moieties did not undergo the aza-Michael-addition anymore. These results may have wider implications for the 1,4-addition of guanidines to α,β-unsaturated carbonyl compounds, particularly to didehydro amino acids.     

Spot arrays on modified glass surfaces for efficient SPOT synthesis and on-chip bioassay of peptides.

To make SPOT synthesis of peptides and their assays on glass surfaces more convenient, a simple method for making spot arrays on a slide glass was designed through patterning with a photoresist and perfluorination followed by amination with various silane compounds and polymers. With these spot-arrayed glass surfaces, we could measure the coupling completion of each Fmoc amino acid on the glass surface by direct fluorescence analysis after fluorescence-labeling the amino groups on the surface of each spot. Then we synthesized several types of decapeptides and HPQ-pentapeptides on the spot-arrayed glasses and identified the optimal surface condition for stepwise peptide coupling and on-chip bioassay. After optimizing the surface conditions, we synthesized a model library of biotin-Gly-Ala-P(1)-Gly (P(1): one of 19 amino acids) and successfully replicated the well-known alpha-chymotrypsin subsite specificities through Cy5-streptavidin binding to the remaining biotin on the surface after the enzymatic digestion.     

The Synthesis of Aminopyri Dine-Based Phosphonoacetates as ADP Analogs

Abstract

The rationale for proposing the title compounds as potential adenosine diphosphate receptor antagonists is discussed. A convenient synthesis and formulation for the cyclopentenyl amino alcohol 8 is described.     

Evaluation and separation of steroid-bovine serum albumin conjugates by high-performance liquid chromatography

The conventional methods for characterization of steroid immunogens are based on the determination of the total amount of hapten bound to the protein carrier either by the UV spectroscopy or titration of unsubstituted amino groups. These methods do not allow more detailed insight into the immunogen composition. HPLC of the immunogen combined with UV detection is a relatively rapid and convenient method enabling determination of the hapten content in each fraction and, eventually, separation of individual fractions differing in the hapten content or purification of crude product.     

Fluorometric quantitation of amino sugars in the picomole range.

A fluorometric method has been developed for the convenient and quantitative assay of amino sugars over the concentration range of 10 nm to 6 mm. Linear results are obtained for reaction mixtures containing 6 pmol to 60 nmol hexosamine. The procedure involves the condensation of amino sugars with the fluorogenic reagent o-phthalaldehyde, at alkaline pH in the presence of 2-mercaptoethanol. Relative fluorescence intensities are then determined using excitation and emission wavelengths of 340 and 455 nm, respectively. The presence of 2-mercaptoethanol in reaction mixtures not only enhanced sensitivity of the assay, but also defined the excitation/emission spectra. Under the conditions described, amino acids were also found to react with o-phthalaldehyde, yielding fluorescence intensities similar to those of amino sugars. These results suggest the applicability of fluorescence techniques in automated amino sugar analyses, as well as the potential interference of other compounds containing primary amines.     

大肠杆菌脂蛋白与CTB-pres2抗原基因的融合及表达

首次采用基因融合方式,在乱毒素B亚基-乙型肝炎病毒Pres2抗原融合基因（ctxB-Pres2）的5’端了引入编码大肠杆菌脂蛋白信号肽及N端九个氨基酸的核苷酸序列,分别置于ctb及lpp／lac启动子下在大肠杆菌中获得分泌性表达．表达的融合蛋白均定位于膜上,并且可以和GM1、抗-CTB抗体及抗HBVPreS2单克隆抗体结合,说明该融合蛋白保留了CTB的基本高级结构及CTB、PreS2抗原的抗原性．3H-棕榈酸标记实验证实该融合蛋白发生脂肪化,为免疫原性研究奠定了基础．此外,还研究了不同信号肽和宿主菌对该蛋白表达的影响．     

Amino acid pyridoxyl esters in peptide synthesis

Pyridoxyl residue was suggested to be used as a multifunctional protective and modifying group in peptide synthesis. The modification was carried out by introducing the pyridoxyl residue in free or partially protected peptides or by the addition of amino acid pyridoxyl esters by the methods of conventional peptide synthesis without the removal of the pyridoxyl group at the terminal stages of the synthesis (the second approach is more convenient). Pyridoxyl residue was also used as a spacer in solid phase peptide synthesis. It was attached to the polymer by the alkylation of the hydroxyl groups or of the pyridine ring of the pyridoxyl derivatives with the chloromethylated styrene-divinylbenzene copolymer (the standard Merrifield resin). Potentials for the use of pyridoxyl derivatives in the synthesis of linear, multiplet, and cyclic peptides are discussed.     

Pyridoxyl amino acid esters in peptide synthesis

Pyridoxyl residue was suggested to be used as a multifunctional protective and modifying group in peptide synthesis. The modification was carried out by introducing the pyridoxyl residue in free or partially protected peptides or by the addition of amino acid pyridoxyl esters by the methods of conventional peptide synthesis without the removal of the pyridoxyl group at the terminal stages of the synthesis (the second approach is more convenient). Pyridoxyl residue was also used as a spacer in solid phase peptide synthesis. It was attached to the polymer by the alkylation of the hydroxyl groups or of the pyridine ring of the pyridoxyl derivatives with the chloromethylated styrene-divinylbenzene copolymer (the standard Merrifield resin). Potentials for the use of pyridoxyl derivatives in the synthesis of linear, multiplet, and cyclic peptides are discussed.