Trapping of excess electrons at the microhydrated protonated amino groups in proteins

2012 ◽  
Vol 136 (10) ◽  
pp. 105101 ◽  
Author(s):  
Wenchao Li ◽  
Zhenwei Zhang ◽  
Hongfang Yang ◽  
Xiuxiu Wu ◽  
Jinxiang Liu ◽  
...  
Keyword(s):  
Amino Groups ◽  
Excess Electrons

Aldehyde gold clusters for molecular labeling

1995 ◽  
Vol 53 ◽  
pp. 858-859
Author(s):  
James F. Hainfeld ◽  
Frederic R. Furuya
Keyword(s):  
Covalent Bond ◽  
Aldehyde Group ◽  
Gold Clusters ◽  
Side Reactions ◽  
Amino Groups ◽  
Sodium Cyanoborohydride ◽  
Schiff’S Base ◽  
Protein Molecules ◽  
Hydroxysuccinimide Esters ◽  
Primary Amino

Glutaraldehyde is a useful tissue and molecular fixing reagents. The aldehyde moiety reacts mainly with primary amino groups to form a Schiff's base, which is reversible but reasonably stable at pH 7; a stable covalent bond may be formed by reduction with, e.g., sodium cyanoborohydride (Fig. 1). The bifunctional glutaraldehyde, (CHO-(CH2)3-CHO), successfully stabilizes protein molecules due to generally plentiful amines on their surface; bovine serum albumin has 60; 59 lysines + 1 α-amino. With some enzymes, catalytic activity after fixing is preserved; with respect to antigens, glutaraldehyde treatment can compromise their recognition by antibodies in some cases. Complicating the chemistry somewhat are the reported side reactions, where glutaraldehyde reacts with other amino acid side chains, cysteine, histidine, and tyrosine. It has also been reported that glutaraldehyde can polymerize in aqueous solution. Newer crosslinkers have been found that are more specific for the amino group, such as the N-hydroxysuccinimide esters, and are commonly preferred for forming conjugates. However, most of these linkers hydrolyze in solution, so that the activity is lost over several hours, whereas the aldehyde group is stable in solution, and may have an advantage of overall efficiency.

The Action of Thrombin on Modified Fibrinogen

1983 ◽  
Vol 49 (03) ◽  
pp. 208-213
Author(s):  
A J Osbahr
Keyword(s):  
Physical Properties ◽  
Negative Charge ◽  
Lysine Residue ◽  
Fibrinopeptide A ◽  
Amino Groups ◽  
Lysine Residues ◽  
Citraconic Anhydride

SummaryThe modification of canine fibrinogen with citraconic anhydride modified the ε-amino groups of the fibrinogen and at the same time generated additional negative charges into the protein. The addition of thrombin to the modified fibrinogen did not induce polymerization; however, the fibrinopeptide was released at a faster rate than from the unmodified fibrinogen. The physical properties of the citraconylated fibrinogen were markedly altered by the modification of 50-60 lysine residues in one hour. A modified fibrinopeptide-A was released by thrombin from the modified fibrinogen and was electrophoretically more anionic than the unmodified fibrinopeptide-A. Edman analysis confirmed the modification of the lysine residue present in the peptide. The rate of removal of citraconylated fibrinopeptide-A from modified fibrinogen by thrombin was 30 to 40 percent greater than the cleavage of unmodified fibrinopeptide-A from unmodified fibrinogen. However, the modification of 60 or more lysine residues in the fibrinogen produced a decrease in the rate of cleavage of citraconylated fibrinopeptide-A. The results suggest that additional negative charge in the vicinity of the attachment of fibrinopeptide-A to canine fibrinogen aids in the removal of the peptide by thrombin.

COMPARATIVE STUDIES OF THE POTENTIATION OF CORTICOTROPHIN ACTIVITY BY SEVERAL INACTIVE DERIVATIVES

1963 ◽  
Vol 42 (2) ◽  
pp. 209-213 ◽  
Author(s):  
Arthur I. Cohen ◽  
Edward H. Frieden
Keyword(s):  
Biological Activity ◽  
Comparative Studies ◽  
Free Amino ◽  
Hormonal Activity ◽  
Amino Groups

ABSTRACT A number of corticotrophin analogues have been prepared, some of which potentiate the biological activity of the untreated hormone in vitro. The free amino groups of corticotrophin appear to be essential not only for hormonal activity, but also for the interaction of the analogues with the tissue corticotrophin inactivating system which is assumed to account for the potentiating effect.

Biphenyl-Derivatives Possessing Tertiary Amino Groups as β-Secretase (BACE1) Inhibitors

2010 ◽  
Vol 7 (7) ◽  
pp. 507-515
Author(s):  
Simone Bertini ◽  
Elisa Ghilardi ◽  
Valentina Asso ◽  
Carlotta Granchi ◽  
Filippo Minutolo ◽  
...  
Keyword(s):  
Amino Groups ◽  
Tertiary Amino

Chitosan Nanoparticles: An Approbative System for the Delivery of Herbal Bioactives

2020 ◽  
Vol 10 ◽  
Author(s):  
Sapna Saini ◽  
Sanju Nanda ◽  
Anju Dhiman
Keyword(s):  
Drug Delivery ◽  
Drug Delivery Systems ◽  
State Of The Art ◽  
Chitosan Nanoparticles ◽  
Delivery Systems ◽  
Intrinsic Properties ◽  
Amino Groups ◽  
Suitable Candidate ◽  
Film Forming ◽  
Novel Drug

: Chitosan, a natural biodegradable polymer obtained from deacetylation of chitin, has been used as an approbative macromolecule for the development of various novel drug delivery systems. It is one of the most favorable biodegradable carriers for nanoparticulate drug delivery due to its intrinsic properties, such as biocompatibility, biodegradability, non-toxicity, availability of free reactive amino groups, and ease of chemical modification into different active derivatives. Furthermore, interesting physical properties (film-forming, gelling and thickening) make it a suitable candidate for formulations, such as films, microcapsules, beads, nanoparticles, nanofibres, nanogel and so on. Researchers have reported that chitosan nanoparticles act as a promising vehicle for herbal actives as they provide a superior alternative to traditional carriers and improve pharmaceutical efficiency. As no review of chitosan nanoparticles encapsulating herbal extracts and bioactives has been published till date, a maiden effort has been made to collate and review the use of chitosan nanoparticles for the entrapment of phytoconstituents to yield stable, efficient and safe drug delivery systems. Additionally, the paper presents a comprehensive account of the state-of the-art in fabricating herbal chitosan nanoparticles and their current pharmacological status. A list of patents on chitosan nanoparticles of herbal actives has also been included. This review is intended to serve as a didactic discourse for the formulation scientists endeavoring to develop advanced delivery systems for herbal actives.

[1-β-Mercaptopropionic acid, 8-norarginine]vasopressin and [1-β-mercaptopropionic acid, 8-D-norarginine]vasopressin. Two analogs with strong biological effects

1979 ◽  
Vol 44 (4) ◽  
pp. 1179-1186 ◽  
Author(s):  
Milan Zaoral ◽  
František Brtník ◽  
Martin Flegel ◽  
Tomislav Barth ◽  
Alena Machová
Keyword(s):  
Biological Effects ◽  
Disulfide Bridge ◽  
Protecting Groups ◽  
Pressor Effect ◽  
Amino Groups ◽  
Mercaptopropionic Acid ◽  
Antidiuretic Effect ◽  
Carbodiimide Method

[1-β-Mercaptopropionic acid, 8-norarginine]vasopressin (L8, D8; I, II) was prepared by condensation of β-benzylthiopropionyl-tyrosyl-phenylalanyl-glutaminyl-asparaginyl-S-benzylcysteine with Nγ-benzyloxycarbonyl-α,γ-diaminobutyryl-glycine amide (L2, D2) by the azide or carbodiimide method, respectively, removal of the benzyloxycarbonyl residue, guanidination of γ-amino groups, removal of protecting groups, closing of the disulfide bridge, and electrophoretic purification. I has an almost 2 times higher antidiuretic effect than DDAVP and a 3 times higher pressor effect than AVP. II has 20-25% of the antidiuretic effect of DDAVP and 16 IU/mg of the pressor effect.

Axially Chiral Bis(α-amino Acid)s and Their Deamino Analogues. Synthesis and Configurational Assignment

1998 ◽  
Vol 63 (2) ◽  
pp. 211-221 ◽  
Author(s):  
Miloš Tichý ◽  
Luděk Ridvan ◽  
Miloš Buděšínský ◽  
Jiří Závada ◽  
Jaroslav Podlaha ◽  
...  
Keyword(s):  
Amino Acid ◽  
Nmr Spectra ◽  
Building Blocks ◽  
X Ray Diffraction ◽  
Amino Groups ◽  
X Ray ◽  
Configurational Assignment ◽  
Symmetry Properties ◽  
Axially Chiral ◽  
Polymeric Structures

The axially chiral bis(α-amino acid)s cis-2 and trans-2 as possible building blocks for polymeric structures of novel type of helicity were prepared. Their configuration has been determined by NMR spectroscopy and, in the case of the trans-isomer, confirmed by single-crystal X-ray diffraction. Analogous pair of stereoisomeric diacids cis-3 and trans-3, devoid of the amino groups, was also prepared and their configuration assigned. The observed differences in the NMR spectra of cis- and trans-isomers of 2 and 3 are discussed from the viewpoint of their different symmetry properties.

Purification of Penicillin Amidohydrolase, an Enzyme for Semisynthetic Procedures

1992 ◽  
Vol 57 (10) ◽  
pp. 2187-2191 ◽  
Author(s):  
Jiří Jiráček ◽  
Tomislav Barth ◽  
Jiří Velek ◽  
Ivo Bláha ◽  
Jan Pospíšek ◽  
...  
Keyword(s):  
Affinity Chromatography ◽  
Amino Groups ◽  
Primary Amino

Penicillin amidohydrolase (EC 3.5.1.11.) is one of the few enzymes used successfully for deprotection of primary amino groups of semisynthetic peptides. The available material is usually contamined by endo- and exopeptidases. We managed to prepare the enzyme devoid of trypsin- and chymotrypsin-like activities using affinity chromatography with specific ligands: Gly-D-Phe-Phe-Tyr-Thr-Pro-Lys-Thr (the fF peptide) and Leu-Gly-Val-D-Arg-Arg-Gly-Phe (the rR peptide). For further purification of the enzyme affinity chromatography with N-phenylacetyl-D-tert-Leu as a ligand was used.

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