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Primary Amino Groups (primary + amino_groups)
Selected AbstractsExtraction of native collagen from limed bovine split wastes through improved pretreatment methodsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2008Dong Li Abstract BACKGROUND: The large amount of limed bovine split wastes discharged by the leather industry has raised concerns regarding their environmental effect. The objective of this work was to perform pilot plant trials to extract high-value native collagen from these wastes through improved pretreatment methods. RESULTS: EDTA- and HCl-pretreatment gave similar removal percentages of inorganic substances. Owing to the open structure of fibers, the collagen yield of HCl-pretreated splits (HPS) (41.31%) was higher than that of EDTA-pretreated splits (EPS) (10.42%). Furthermore, HCl-pretreated split collagen (HPC) had a more acidic isoelectric point, lower content of primary amino groups, larger Z-average particle size and higher relative viscosity than EDTA-pretreated split collagen (EPC). Electrophoretic analysis and circular dichroism spectra revealed the maintenance of polypeptide and triple helix conformation, respectively. In addition, the transition temperatures of EPC (34.7 °C) and HPC (34.6 °C) detected by differential scanning calorimetry (DSC) were close to that of commercial collagen from calfskin (CCC) (35.7 °C). CONCLUSION: A process of native collagen extraction from limed bovine split wastes was proposed. While both EPC and HPC represented similar physicochemical properties to those of CCC, the collagen yield of HPS was much higher than that of EPS. Copyright © 2008 Society of Chemical Industry [source] Improved Method for Determining Food Protein Degree of HydrolysisJOURNAL OF FOOD SCIENCE, Issue 5 2001P.M. Nielsen ABSTRACT When producing hydrolyzed proteins, it is important to determine the degree of hydrolysis (DH). The trinitro-benzene-sulfonic acid (TNBS) method is well established with regard to enzymatic hydrolysis. However, this method is laborious, cannot be used to follow a hydrolysis reaction continuously, and includes hazardous and unstable chemicals. This paper describes a method based on the reaction of primary amino groups with o-phthaldialdehyde (OPA). The conclusion is that the OPA method of analyzing the DH of protein hydrolyses is more accurate, is easier and faster to carry out, has a broader application range, and is environmentally safer than the TNBS method. [source] Chemical cross-linking with NHS esters: a systematic study on amino acid reactivitiesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2009Stefanie Mädler Abstract Structure elucidation of tertiary or quaternary protein structures by chemical cross-linking and mass spectrometry (MS) has recently gained importance. To locate the cross-linker modification, dedicated software is applied to analyze the mass or tandem mass spectra (MS/MS). Such software requires information on target amino acids to limit the data analysis time. The most commonly used homobifunctional N-hydroxy succinimide (NHS) esters are often described as reactive exclusively towards primary amines, although side reactions with tyrosine and serine have been reported. Our goal was to systematically study the reactivity of NHS esters and derive some general rules for their attack of nucleophilic amino acid side chains in peptides. We therefore studied the cross-linking reactions of synthesized and commercial model peptides with disuccinimidyl suberate (DSS). The first reaction site in all cases was expectedly the ,-NH2 -group of the N -terminus or the ,-NH2 -group of lysine. As soon as additional cross-linkers were attached or loops were formed, other amino acids were also involved in the reaction. In addition to the primary amino groups, serine, threonine and tyrosine showed significant reactivity due to the effect of neighboring amino acids by intermediate or permanent Type-1 cross-link formation. The reactivity is highly dependent on the pH and on adjacent amino acids. Copyright © 2009 John Wiley & Sons, Ltd. [source] Characterization of ring-opening polymerization of genipin and pH-dependent cross-linking reactions between chitosan and genipinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2005Fwu-Long Mi Abstract In this study, a novel chitosan-based polymeric network was synthesized by crosslinking with a naturally occurring crosslinking agent,genipin. The results showed that the crosslinking reactions were pH-dependent. Under basic conditions, genipin underwent a ring-opening polymerization prior to crosslinking with chitosan. The crosslink bridges consisted of polymerized genipin macromers or oligomers (7 , 88 monomer units). This ring-opening polymerization of genipin was initiated by extracting proton from the hydroxyl groups at C-1 of deoxyloganin aglycone, followed by opening the dihydropyran ring to conduct an aldol condensation. At neutral and acidic conditions, genipin reacted with primary amino groups on chitosan to form heterocyclic amines. The heterocyclic amines were further associated to form crosslinked networks with short chains of dimmer, trimer, and tetramer bridges. An accompanied reaction of nucleophilic substitution of the ester group on genipin by the primary amine group on chitosan would occur in the presence of an acid catalysis. The extent in which chitosan gels crosslinked with genipin was significantly dependent on the crosslinking pH values: 39.9 ± 3.8% at pH 5.0, 96.0 ± 1.9% at pH 7.4, 45.4 ± 1.8% at pH 9.0, and 1.4 ± 1.0% at pH 13.6 (n = 5, p < 0.05). Owing to the different crosslinking extents and different chain lengths of crosslink bridges, the genipin-crosslinked chitosan gels showed significant difference in their swelling capability and their resistance against enzymatic hydrolysis, depending on the pH conditions for crosslinking. These results indicated a direct relationship between the mode of crosslinking reaction, and the swelling and enzymatic hydrolysis properties of the genipin-crosslinked chitosan gels. The ring-opening polymerization of genipin and the pH-dependent crosslinking reactions may provide a novel way for the preparation and exploitation of chitosan-based gels for biomedical applications. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1985,2000, 2005 [source] Synthesis of poly(L -lactide)-grafted pullulan through coupling reaction between amino group end-capped poly(L -lactide) and carboxymethyl pullulan and its aggregation behavior in waterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2004Tatsuro Ouchi Abstract Poly(L -lactide) (PLLA) with terminal primary amino groups (PLLA-NH2) was synthesized and used to construct PLLA-grafted pullulan (Pul- g -PLLA). It consisted of a hydrophilic carboxymethyl Pul (CM-Pul) main chain and hydrophobic PLLA graft chains that were created through a direct coupling reaction between PLLA-NH2 and CM-Pul using 2-ethoxy-1-(ethoxycarbonyl)-1,2-dihydroquinoline as a condensation reagent. Pul- g -PLLAs with over 78 wt % sugar unit content were found to form nanometer-sized aggregates in water. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5482,5487, 2004 [source] Protein labeling by iTRAQ: A new tool for quantitative mass spectrometry in proteome researchPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2007Sebastian Wiese Abstract A novel, MS-based approach for the relative quantification of proteins, relying on the derivatization of primary amino groups in intact proteins using isobaric tag for relative and absolute quantitation (iTRAQ) is presented. Due to the isobaric mass design of the iTRAQ reagents, differentially labeled proteins do not differ in mass; accordingly, their corresponding proteolytic peptides appear as single peaks in MS scans. Because quantitative information is provided by isotope-encoded reporter ions that can only be observed in MS/MS spectra, we analyzed the fragmentation behavior of ESI and MALDI ions of peptides generated from iTRAQ-labeled proteins using a TOF/TOF and/or a QTOF instrument. We observed efficient liberation of reporter ions for singly protonated peptides at low-energy collision conditions. In contrast, increased collision energies were required to liberate the iTRAQ label from lysine side chains of doubly charged peptides and, thus, to observe reporter ions suitable for relative quantification of proteins with high accuracy. We then developed a quantitative strategy that comprises labeling of intact proteins by iTRAQ followed by gel electrophoresis and peptide MS/MS analyses. As proof of principle, mixtures of five different proteins in various concentration ratios were quantified, demonstrating the general applicability of the approach presented here to quantitative MS-based proteomics. [source] Selective isolation of multiple positively charged peptides for 2-DE-free quantitative proteomicsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 16 2006Aniel Sánchez Abstract A method for quantitative proteomic analysis based on the selective isolation of multiply charged peptides (RH peptides) containing arginine and histidine residues is described. Two pools of proteins are digested in tandem with lysyl-endopeptidase and trypsin and the primary amino groups of proteolytic peptides are separately labeled with d3 - and d0 -acetic anhydride. This reaction has a dual purpose: (i) to allow the relative protein quantification in two different conditions and (ii) to restrict the positive charges of peptides to the presence of arginine and histidine. The N -acylated peptides are separated by cation-exchange chromatography into two groups, neutral and singly charged peptides (R,+,H,,,1) that are neither retained nor analyzed, whereas the multiply charged peptides (R,+,H>1) are retained into the column and can be eluted in batch or further fractionated using a saline gradient before LC-MS/MS analysis. In silico analysis revealed that the selective isolation of RH peptides considerably simplifies the complex mixture of peptides (three RH peptides/protein) and at the same time they represent 84% of the whole proteomes. The selectivity, and recovery of the method were evaluated with model proteins and with a complex mixture of proteins extracted from Vibrio cholerae. [source] | ||||||||||