scholarly journals Relationship between isoelectric point of native and chemically modified insulin and liposomal fusion

1989 ◽  
Vol 264 (1) ◽  
pp. 285-287 ◽  
Author(s):  
R N Farías ◽  
A E López Viñals ◽  
E Posse ◽  
R D Morero
Keyword(s):  
Methyl Ester ◽  
Isoelectric Point ◽  
Carboxyl Groups ◽  
Amino Groups ◽  
Chemically Modified ◽  
Glycine Methyl Ester ◽  
Native Insulin ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Fusion Ability

Native insulin causes fusion of negatively charged liposomes in the pH range from 3.0 to 5.5. In marked contrast, insulin with all three amino groups succinylated did not show fusion ability at any pH. On the other hand, insulin amidated with glycine methyl ester with all six carboxyl groups blocked shifted its activity to higher pH, showing a pH range of activity from 3.0 to 7.4. When the carboxyl groups were recovered by hydrolysis of methoxyl groups from glycine methyl ester-treated insulin, the protein obtained (glycyl-insulin with six free carboxyl groups) behaved as native insulin. A good correlation between the isoelectric point values of insulin and its derivatives and their fusion properties was found.

scholarly journals Chemically modified nylons as supports for enzyme immobilization. Polyisonitrile-nylon

1974 ◽  
Vol 143 (3) ◽  
pp. 497-509 ◽  
Author(s):  
Leon Goldstein ◽  
Amihay Freeman ◽  
Mordechai Sokolovsky
Keyword(s):  
Aqueous Medium ◽  
Enzyme Immobilization ◽  
Functional Group ◽  
Carboxyl Groups ◽  
Partial Hydrolysis ◽  
Amino Groups ◽  
Tyrosine Residues ◽  
Chemically Modified ◽  
Reactive Groups ◽  
Hydrolysis Of

Four-component condensations between amine, carboxyl, isocyanide and aldehyde lead to the formation of N-substituted amides (Ugi, 1962). The present paper describes the use of such condensations for the introduction of chemically reactive groups on to the polyamide backbone of nylon. Polyisonitrile-nylon was synthesized by partial hydrolysis of nylon-6 powder, followed by resealing of the newly formed −CO2... NH2− pairs via a four-component condensation, by using acetaldehyde and 1,6-di-isocyanohexane. Polyisonitrile-nylon could also be converted into a diazotizable arylamino derivative, polyaminoaryl-nylon, by a four-component condensation by using a bifunctional amine, pp′-diaminodiphenylmethane, in the presence of an aldehyde and a carboxylate compound. The versatility of four-component condensations involving the isocyanide functional group of polyisonitrile-nylon allowed coupling of proteins, in an aqueous medium at neutral pH, through either their amino or carboxyl groups. Trypsin and papain were bound to polyisonitrile-nylon through their amino groups by a four-component condensation by using acetaldehyde and acetate; conversely, succinyl-(3-carboxypropionyl-)trypsin, pepsin and papain were coupled through their carboxyl groups in the presence of acetaldehyde and an amine (Tris). Diazotized polyaminoaryl-nylon could be utilized for the immobilization of papain, via the tyrosine residues of the enzyme.

THE ACETYLATION OF THROMBIN

1959 ◽  
Vol 37 (1) ◽  
pp. 1361-1366 ◽  
Author(s):  
Ricardo H. Landaburu ◽  
Walter H. Seegers
Keyword(s):  
Methyl Ester ◽  
Proteolytic Activity ◽  
Basic Structure ◽  
Amino Groups ◽  
Spontaneous Hydrolysis ◽  
Optimum Ph ◽  
Hydrolysis Of

Purified thrombin-C loses its clotting power upon acetylation. The thrombin-E which is produced during the acetylation has approximately twice the proteolytic activity as the original thrombin-C. Evidently amino groups are not necessary to have thrombin-E activity, but if o-acyl groups are also produced the enzyme does not hydrolyze p-toluenesulphonylarginine methyl ester (TAMe). The activity can be recovered by spontaneous hydrolysis of the o-acyl groups at pH 8.5. Thrombin-E does not activate fibrinogen, but does lyse fibrin. The optimum pH with TAMe as substrate is 8.8. It may be that thrombin-C is a dimer of the basic structure in thrombin-E.

Kinetic properties of the α-lytic protease of Sorangium sp., a bacterial homologue of the pancreatopeptidases

1969 ◽  
Vol 47 (3) ◽  
pp. 305-316 ◽  
Author(s):  
H. Kaplan ◽  
D. R. Whitaker
Keyword(s):  
Methyl Ester ◽  
Catalytic Properties ◽  
Substrate Binding ◽  
Kinetic Properties ◽  
Histidine Residue ◽  
Amino Groups ◽  
Binding Properties ◽  
Histidine Residues ◽  
Support Reaction ◽  
Hydrolysis Of

The kinetics under consideration are those of a bacterial serine protease with the same "active serine" sequence as chymotrypsin, trypsin, and elastase, and with a single histidine residue in a sequence which closely matches the sequences around histidine-57 of chymotrypsin and the analogous histidine residues of trypsin and elastase. In agreement with previous evidence of an elastase-like specificity, esters of N-substituted, neutral, aliphatic L-amino acids proved to be good to excellent substrates for the α-enzyme; esters of arginine, tyrosine, and tryptophan were not hydrolyzed. The enzyme has a much higher activity than the pancreatopeptidases towards p-nitrophenyl acetate and p-nitrophenyl trimethyl acetate; the catalytic rate coefficient kc for the latter substrate is about fivefold greater than that of elastase.The catalytic properties match those of the pancreatopeptidases in the following respects. As demonstrated with N-acetyl-L-valine methyl ester as substrate, kc is dependent on an ionization with a pKa of 6.7 in water and 7.3 in H22O; Δ log (kc/Km)/ΔpH for this ionization is equal to 1.0; kc is reduced 50% when H2O is replaced by H22O. These findings are consistent with a requirement for a single unprotonated histidine residue and general basic catalysis by that residue. The burst of p-nitrophenol in hydrolyses of p-nitrophenyl trimethyl acetate is proportional to [E]0; the magnitude of the proportionality factor and the rate of attainment of a steady state are consistent with the condition [Formula: see text], as in chymotrypsin kinetics. Thus the purely catalytic properties of the α-enzyme match those of chymotrypsin very closely. These findings do not support reaction mechanisms which require two catalytically functional histidine residues for such catalysis. The substrate-binding properties of the α-enzyme differ from those of chymotrypsin in that substrate binding does not depend on ionization of an N-terminal α-amino group; Km for the hydrolysis of N-acetyl-L-valine methyl ester is constant from pH 5 to pH 10 and enzymatic activity is unaffected by acetylation of the enzyme's α- and ε-amino groups. Ks for the hydrolysis of p-nitrophenyl trimethyl acetate is appreciably greater than the Ks of elastase for this substrate.The chloromethyl ketones of glycine and valine did not inhibit the enzyme or alkylate its histidine residue.

scholarly journals Positive Charges on Lysine Residues of the Extrinsic 18 kDa Protein Are Important to Its Electrostatic Interaction with Spinach Photosystem II Membranes

2005 ◽  
Vol 37 (11) ◽  
pp. 737-742 ◽  
Author(s):  
Jin-Peng Gao ◽  
Zhen-Hua Yong ◽  
Feng Zhang ◽  
Kang-Cheng Ruan ◽  
Chun-He Xu ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Methyl Esters ◽  
Binding Activity ◽  
Water Soluble ◽  
Carboxyl Groups ◽  
Amino Groups ◽  
Charged Amino Acids ◽  
Lysine Residues ◽  
Glycine Methyl Ester ◽  
Positively Charged

Abstract To determine the contribution of charged amino acids to binding with the photosystem II complex (PSII), the amino or carboxyl groups of the extrinsic 18 kDa protein were modified with Nsuccinimidyl propionate (NSP) or glycine methyl ester (GME) in the presence of a water-soluble carbodiimide, respectively. Based on isoelectric point shift, 4–10 and 10–14 amino groups were modified in the presence of 2 and 4 mM NSP, respectively. Similarly, 3–4 carboxyl groups were modified by reaction with 100 mM GME. Neutralization of negatively charged carboxyl groups with GME did not alter the binding activity of the extrinsic 18 kDa protein. However, the NSP-modified 18 kDa protein, in which the positively charged amino groups had been modified to uncharged methyl esters, failed to bind with the PSII membrane in the presence of the extrinsic 23 kDa protein. This defect can not be attributed to structural or conformational alterations imposed by chemical modification, as the fluorescence and circular dichroism spectra among native, GME and NSP-modified extrinsic 18 kDa proteins were similar. Thus, we have concluded that the positive charges of lysyl residues in the extrinsic 18 kDa protein are important for its interaction with PSII membranes in the presence of the extrinsic 23 kDa protein. Furthermore, it was found that the negative charges of carboxyl groups of this protein did not participate in binding with the extrinsic 23 kDa protein associated with PSII membranes.

Sequence Determination of a Protein with N-Terminal Glutamic Acid after Modification of Carboxyl Groups with Carbodiimide as the Coupling Agent

1974 ◽  
Vol 52 (6) ◽  
pp. 560-562
Author(s):  
C. Gilardeau ◽  
M. Chrétien
Keyword(s):  
Methyl Ester ◽  
Glutamic Acid ◽  
Water Soluble ◽  
Carboxyl Groups ◽  
Edman Degradation ◽  
Sequence Determination ◽  
Glutamic Acid Residue ◽  
N Terminus ◽  
Glycine Methyl Ester

Glutamine and asparagine residues in proteins can be differentiated from glutamic and aspartic residues, during the Edman degradation, after modification of the carboxyl groups by glycine methyl ester in presence of a water-soluble carbodiimide. When applied to ovine and porcine beta-lipotropic hormones, which have a glutamic acid residue at the N-terminus, the carbodiimide blocks the N-terminus. However, the Edman degradation proceeds normally, if the phenylthiocarbamyl derivative is formed prior to the modification reaction with glycine. In this communication, radioactive glycine was used to modify the carboxyl groups.

Intramolecular Catalysis of Dialkyl ω-Aminoalkylphosphonate Hydrolysis

1994 ◽  
Vol 47 (3) ◽  
pp. 545 ◽  
Author(s):  
DR Leslie ◽  
S Pantelidis
Keyword(s):  
Product Distribution ◽  
Base Catalysis ◽  
Additional Contribution ◽  
Amino Groups ◽  
Intramolecular Catalysis ◽  
General Base ◽  
Secondary Amino ◽  
Tertiary Amino ◽  
Ph Range ◽  
Hydrolysis Of

The influence that intramolecular catalysis of hydrolysis of O-alkyl S-[2-( dialkylamino )ethyl] alkylphosphonothioates by amino groups may have on the product distribution of the reaction is investigated by study of a series of model compounds. The hydrolysis of diethyl [ω-( ethylamino )alkyl] phosphonates and diethyl [ω-( diethylamino )alkyl] phosphonates has been investigated at 75°C over the pH range 8.21-11.45. Contributions to hydrolysis of the ethoxy groups by intramolecular catalysis by the amino groups have been identified for [2-(amino)ethyl]- and [3-(amino) propyl ]- phosphonates. Secondary and tertiary amino groups assist hydrolysis through general base catalysis. An additional contribution to hydrolysis of the secondary amino compounds by intramolecular nucleophilic catalysis is also observed.

THE ACETYLATION OF THROMBIN

1959 ◽  
Vol 37 (11) ◽  
pp. 1361-1366 ◽  
Author(s):  
Ricardo H. Landaburu ◽  
Walter H. Seegers
Keyword(s):  
Methyl Ester ◽  
Proteolytic Activity ◽  
Basic Structure ◽  
Amino Groups ◽  
Spontaneous Hydrolysis ◽  
Optimum Ph ◽  
Hydrolysis Of

Purified thrombin-C loses its clotting power upon acetylation. The thrombin-E which is produced during the acetylation has approximately twice the proteolytic activity as the original thrombin-C. Evidently amino groups are not necessary to have thrombin-E activity, but if o-acyl groups are also produced the enzyme does not hydrolyze p-toluenesulphonylarginine methyl ester (TAMe). The activity can be recovered by spontaneous hydrolysis of the o-acyl groups at pH 8.5. Thrombin-E does not activate fibrinogen, but does lyse fibrin. The optimum pH with TAMe as substrate is 8.8. It may be that thrombin-C is a dimer of the basic structure in thrombin-E.

scholarly journals Inhitive ability collagenase of N-(cinnamyl) chitooligosaccharide derivative

2017 ◽  
Vol 20 (K3) ◽  
pp. 83-91
Author(s):  
Xuan Minh Le ◽  
Khanh Duy Nguyen ◽  
Khoa Dang Tran ◽  
Tuan Quoc Tran ◽  
Nghiep Dai Ngo
Keyword(s):  
Molecular Weight ◽  
Room Temperature ◽  
Positive Control ◽  
Living Systems ◽  
Amino Groups ◽  
Animal Cells ◽  
Chemically Modified ◽  
Mtt Method ◽  
Hydrolysis Of ◽  
Derivatives Of

Chitooligosaccharides (COS) with molecular weight 4633 Da and 84.67% of deacetylation were synthesized by hydrolysis of chitosan by cellulase at room temperature (33 ± 1 ° C). This COS, then, were chemically modified by grafting cinnamaldehyde at amino groups on the COS. Derivatives of N- (cinnamyl) chitooligosaccharides (CCOS) synthesized with 50.64% of yield and 72.22% of extent of substitution had inhibitory activity enzyme collagenase (a group of matrix metalloproteinases, enzyme family related to metastatic ability of cancer). Compared with the positive control, 58.23% of the effective to inhibit collagenase of CCOS at 1000 μg/ml concentrate. In addition, the CCOS cytotoxicity of CCOS was also assessed by MTT method, the results showed that non-toxic derivatives of animal cells and thus can be tested and applied in living systems.

scholarly journals Electrokinetic properties of chemically modified jute fabrics

2020 ◽  
pp. 69-69
Author(s):  
Aleksandra Ivanovska ◽  
Mirjana Kostic
Keyword(s):  
Zeta Potential ◽  
Isoelectric Point ◽  
Carboxyl Groups ◽  
Chemical Modifications ◽  
Electrokinetic Properties ◽  
Chemically Modified ◽  
Ph Values ◽  
Electrochemical Double Layer ◽  
Jute Fabrics ◽  
Oxidatively Modified

This work aims to study the alkali and oxidatively modified jute fabrics? electrokinetic properties. In contrast to control fabric, chemically modified jute fabrics have a small positive zeta potential in a basic pH range which can be attributed to the presence of sodium cations (originating from mentioned chemical modifications) on their surfaces. At lower pH values, samples modified under milder alkali and oxidative conditions have about 2.2-3.5 times lower zeta potential since the protonation process leads to the formation of higher positive charge in the electrochemical double layer causing higher adsorption of Cl- ions (originating from the electrolyte). On the other hand, more intensive chemical modifications increased the zeta potential at lower pH values due to the increased amount of carboxyl groups and fibers? ability for water retention and hence swelling. The isoelectric point of fabrics having lower zeta potential than control fabric was shifted toward higher pH values pointing out lower contribution of fabrics? surface acidic groups. In the case of extensive oxidation conditions (60 and 90 min), the isoelectric point was shifted toward lower pH values as a result of lignina removal and mentioned higher availability of newly formed carboxyl groups.

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