It is of theoretical and practical significance to understand the mechanism of enzyme adaptation to acidic and alkaline environments and classification of them based on sequence information. In present work, the amino acid composition of 105 acidic and 111 alkaline enzyme sequences was systematically analyzed. Acidic enzymes contained significantly more Trp, Tyr, Thr and Ser, whereas less Glu, Lys, Met and Arg. On the other hand, alkaline enzymes have slightly more Trp, Ala and Cys, whereas less Lys, Arg and Glu. The amount of Ala, Glu, Leu, Asn, Arg, Ser and Thr in acidic and alkaline enzymes varied largely. Hence, a weighted amino acid composition method was developed for the discrimination of acidic and alkaline enzymes. Using the back-check and the 5-fold cross validation methods, the overall accuracy could reach 86.1% and 83.3%, respectively. A new method to classify acidic and alkaline enzymes based on their sequences was established.
Amino Acids ; chemistry ; genetics ; Enzymes ; chemistry ; classification

In the flowers of Sambicus nigra, flavonoids, amino acids and sugars were determined. Among them the main components were flavonoids, which accounted for 7,19±0,10%. From total flavonoid extracts, ,2 compounds were isolated by column chromatography and identified by UV,MS,and NMR spectroscope as quercetin-3-α rhamnopyranosyl- β -glucopyranose and quercetin
Chemistry ; Flowers ; Flavonoids ; Amino Acids ; Carbohydrates

Genetic code expansion (GCE) allows the incorporation of unnatural amino acids into proteins via using stop codons. GCE may achieve site-specific labeling of proteins in combination with the click reaction. Compared with other labeling tools such as fluorescent proteins and tagged antibodies, the compound molecules used in protein labeling by GCE technology are smaller, and therefore, may less interfere the conformational structure of proteins. In addition, through click reaction, GCE allows a 1:1 stoichiometric ratio of the target protein molecule and the fluorescent dye, and the protein can be quantified based on the fluorescence intensity. Thus, GCE technology has great advantages in the researches that require the exposition of living cells under high laser power for longer time, for example, in the context of single molecule tracing and super-resolution microscopic imaging. Meanwhile, this technology lays the foundation for improving the accuracy of positioning and molecule counting in the imaging process of living cells. This review summarized the GCE technology and its recent applications in functionally characterizing, labeling and imaging of proteins.
Amino Acids/chemistry* ; Fluorescent Dyes/chemistry* ; Genetic Code ; Proteins/chemistry*

Nanotube titanic acid (NTA) has distinct optical and electrical character, and has photocatalysis character. In accordance with these qualities, NTA was treated with acid so as to enhance its surface activity. Surface structures and surface groups of acid-treated NTA were characterized and analyzed by Transmission Electron Microscope (TEM) and Fourier Transform Infrared Spectrometry (FT-IR). The interaction between acid-treated NTA and amino acids was investigated. Analysis results showed that the lengths of acid-treated NTA became obviously shorter. The diameters of nanotube bundles did not change obviously with acid-treating. Meanwhile, the surface of acid-treated NTA was cross-linked with carboxyl or esterfunction. In addition, acid-treated NTA can catch amino acid residues easily, and then form close combination.
Acetic Acid ; chemistry ; Adsorption ; Amino Acids ; chemistry ; Drug Interactions ; Nanotubes ; chemistry ; Oxides ; chemistry ; Titanium ; chemistry

OBJECTIVETo determine the contents of amino acids in Cornu Cervi Pantotrichum of different specifications for controlling the quality.

METHODThe contents of 18 kinds of amino acids were determined by amino acid analyzer.

RESULTThe correlation coefficients of 18 kinds of amino acids were all greater than 0.997, the average recovery were all between 99.1%-108.1% with RSDs less than 2.0%. All Cornu Cervi Pantotrichum samples of 29 different specifications contained 17 kinds of amino acids and 7 kinds of essential amino acids. The content of total amino acids in wax slices is relative higher. The content in first born antlers is higher than that in reborn antlers.

CONCLUSIONThis method is suitable for the determination of amino acids in Cornu Cervi Pantotrichum, it provides good reference for the quality control of Cornu Cervi Pantotrichum.

Amino Acids ; analysis ; Animals ; Antlers ; chemistry ; Deer ; Medicine, Chinese Traditional

OBJECTIVETo establish the double HPLC fingerprints of water-soluble composition and amino acids precolumn derivative reagent of 13 batches of Isatidis Radix micropower.

METHODThe gradient elution was adopted with Hypersil BDS C18 column (4.6 mm x 250 mm, 5 microm). Water-soluble ingredients were detected with acetonitrile-0.1% phosphoric acid solution as mobile phase, flow rate 0.5 mL x min(-1), column temperature 20 degrees C, and the injection volume 10 microL. Amino acid ingredient were derived by PITC, and then were detected with mobile phase of 0.1 mol x L(-1) sodium acetate buffer solution (pH 6.5) - acetonitrile, flow rate 1.0 mL x min(-1), column temperature 30 degrees C, and the injection volume 5 microL. Both of the absorption wavelengths were 254 nm. Pharmacopoeia Commission "Chinese chromatographic fingerprint evaluation system (version 2.0)" was adopted to analyse, fingerprints of Isatidis Radix micropower were established, at the same time 4 main ingredients were recognized by the SPSS cluster analysis.

RESULTCommon mode of Fingerprint to water-soluble and amino acids ingredient of Isatidis Radix micropower was established, then adenosine, epigoitrin and 15 amino acids were identified as characteristic peaks. Cluster analysis showed that different kinds of the herbal Isatidis Radix micropower from different areas were different levels in the main ingredients.

CONCLUSIONDouble fingerprints of Isatidis Radix micropower is established. Each peak is optimally separated in chromatogram, which provides a scientific basis for quality control of Isatidis Radix micropower.

Amino Acids ; analysis ; Isatis ; chemistry ; Powders ; Quality Control

The α-amino acid ester acyltransferase (SAET) from Sphingobacterium siyangensis is one of the enzymes with the highest catalytic ability for the biosynthesis of l-alanyl-l-glutamine (Ala-Gln) with unprotected l-alanine methylester and l-glutamine. To improve the catalytic performance of SAET, a one-step method was used to rapidly prepare the immobilized cells (SAET@ZIF-8) in the aqueous system. The engineered Escherichia coli (E. coli) expressing SAET was encapsulated into the imidazole framework structure of metal organic zeolite (ZIF-8). Subsequently, the obtained SAET@ZIF-8 was characterized, and the catalytic activity, reusability and storage stability were also investigated. Results showed that the morphology of the prepared SAET@ZIF-8 nanoparticles was basically the same as that of the standard ZIF-8 materials reported in literature, and the introduction of cells did not significantly change the morphology of ZIF-8. After repeated use for 7 times, SAET@ZIF-8 could still retain 67% of the initial catalytic activity. Maintained at room temperature for 4 days, 50% of the original catalytic activity of SAET@ZIF-8 could be retained, indicating that SAET@ZIF-8 has good stability for reuse and storage. When used in the biosynthesis of Ala-Gln, the final concentration of Ala-Gln reached 62.83 mmol/L (13.65 g/L) after 30 min, the yield reached 0.455 g/(L·min), and the conversion rate relative to glutamine was 62.83%. All these results suggested that the preparation of SAET@ZIF-8 is an efficient strategy for the biosynthesis of Ala-Gln.
Escherichia coli/genetics* ; Glutamine ; Zeolites/chemistry* ; Amino Acids

The aim of the paper is to reveals the variations of Dendrobium officinale amino acids in different strains and parts for breeding excellent varieties, and providing scientific basis for the expanding of medicinal or edible parts. The contents of 17 amino acids in 11 strains of D. officinale were determined by hydrochloric acid hydrolysis method. The total amino acids content of leaves was from 6.76 to 7.97 g per 100 g, and the stems was from 1.61 to 2.44 g per 100 g. As the content of amino acids in leaves was significantly higher than that of stems, and the composition was close to the ideal protein standard proposed by FAO/WHO. The leaves of D. officinale had the good prospect for the development of functional foods. The 9 x 66 strain which with high yield and polysaccharide content had the highest amino acids content both in stems and leaves, indicated crossbreeding could improve the quality of varieties. Compared the amino acids content of D. officinale in two main harvest periods, the harvest time has a significant impact on amino acids content of D. officinale. This study demonstrates that the harvesting time of D. officinale stems is suitable for leaves as well, which is the period before bolssom.
Amino Acids ; chemistry ; Dendrobium ; chemistry ; classification ; Drugs, Chinese Herbal ; chemistry ; Phylogeny ; Plant Leaves ; chemistry ; classification

OBJECTIVETo study the extraction, isolation and composition of Lycium barbarum polysaccharides (LBP).

METHODLBP was extracted from L. barbarum with water, isolationed and purified by DEAE ion-exchange cellulose and gel chromatography, and their structural composition was studied by means of SDS-PAGE gel electrophoresis, GC, amino acid automatic analysis, etc.

RESULTPure LBP has four water solubie polysaccharides, M W was 1.524 x 10(5). LBP was composed of 6 kinds of monosaccharides (Ara, Rha, Xyl, Man, Gal and Glc), galacturonic acid and 18 kinds of amino acids.

CONCLUSIONLBP is a kind of complex polysaccharides consisting of acidic heteropolysaccharides and polypeptide or protein, and LBP has Glycan-O-Ser glycopeptide structures.

Amino Acids ; analysis ; Hexuronic Acids ; analysis ; Lycium ; chemistry ; Monosaccharides ; analysis ; Plants, Medicinal ; chemistry ; Polysaccharides ; chemistry ; isolation & purification ; Seeds ; chemistry

Functional designing of natural amino acids (NAA) has received considerable attention in recent years due to its excellent biocompatibility. A novel self-assembling NAA, peptide RAG-16, was designed by hybridizing the characteristic silk fibroin motif (Gly-Ala) with an ionic complementary peptide sequence (Arg-Ala-Asp-Ala) in our study. The self-assembly structure, viscoelastic property, and cyto compatibility of the peptide were investigated by atomic force microscopy, rheometer, Fourier transform infrared spectrum, and inverted fluorescence microscope. RAG-16 was able to form a three-dimensional compact network structure in water. High mechanical performance of the peptide hydrogel was found due to the increase of the silk I structure from inserted fibroin motif segment. Fluorescence staining showed that vast majority of MC3T3-E1 cells in the RAG-16 hydrogel could adhere to, survive, and distribute on different planes. To sum up, in this experiment, the functional designing of the NAA has exhibited its potential application in biomedical field.
Amino Acids ; chemistry ; Biocompatible Materials ; chemistry ; Fibroins ; chemistry ; Hydrogels ; chemistry ; Models, Molecular ; Nanostructures ; chemistry ; ultrastructure ; Peptides ; chemistry ; Silk ; chemistry