scholarly journals Chemical reactivity of the functional groups of insulin. Concentration-dependence studies

1984 ◽  
Vol 217 (1) ◽  
pp. 135-143 ◽  
Author(s):  
H Kaplan ◽  
M A Hefford ◽  
A M L Chan ◽  
G Oda
Keyword(s):  
Functional Groups ◽  
Chemical Reactivity ◽  
Pyrex Glass ◽  
Amino Groups ◽  
High Dilution ◽  
No Adsorption ◽  
Adsorption Effects ◽  
Labelling Procedure ◽  
High Concentrations ◽  
Reaction Vessels

A modification to the competitive labelling procedure of Duggleby and Kaplan [(1975) Biochemistry 14, 5168-5175] was used to study the reactivity of the N-termini, lysine, histidine and tyrosine groups of insulin over the concentration range 1 × 10(-3)-1 × 10(-7)M. Reactions were carried out with acetic anhydride and 1-fluoro-2,4-dinitrobenzene in 0.1 M-KCl at 37 degrees C using Pyrex glass, Tefzel and polystyrene reaction vessels. At high concentrations all groups had either normal or enhanced reactivity but at high dilution the reactivities of all functional groups became negligible. This behaviour is attributed to the adsorption of insulin to the reaction vessels. The histidine residues show a large decrease in reactivity in all reaction vessels in the concentration range 1 × 10(-3)-1 × 10(-5)M where there are no adsorption effects and where the reactivities of all other functional groups are independent of concentration. With polystyrene, where adsorption effects become significant only below 1 × 10(-6)M, the reactivity of the phenylalanine N-terminus also shows a decrease in reactivity between 1 × 10(-5) and 1 × 10(-6)M. In 1 M-KCl insulin does not absorb to Pyrex glass and under these conditions the histidine reactivity is concentration-dependent from 1 × 10(-3) to 5 × 10(-6)M and the B1 phenylalanine alpha-amino and the B29 lysine epsilon-amino reactivities from 5 × 10(-6) to 1 × 10(-7)M, whereas the reactivities of all other groups are constant. These alterations in reactivity on dilution are attributed to disruption of dimer-dimer interactions for histidine and to monomer-monomer interactions for the phenylalanine and lysine amino groups. It is concluded that the monomeric unit of insulin has essentially the same conformation in its free and associated states.

scholarly journals Antifungal Activity and Fourier Transform Infrared Spectrometric Characterization of Aqueous Extracts of Acacia senegal and Acacia tortilis on Phytopathogenic Fungi

2019 ◽  
pp. 1-11
Author(s):  
Al-Otibi Fatimah
Keyword(s):  
Fourier Transform ◽  
Antifungal Activity ◽  
Functional Groups ◽  
Aqueous Extract ◽  
Phytopathogenic Fungi ◽  
Aqueous Extracts ◽  
Acacia Tortilis ◽  
Acacia Senegal ◽  
High Concentrations ◽  
Scanning Electron

Objective: To evaluate the in vitro antifungal activity of aqueous extracts of Acacia senegal (A. senegal) and Acacia tortilis (A. tortilis) against three phytopathogenic fungi (viz., Alternaria alternata [A. alternata], Helminthosporium rostratum [H. rostratum] and Fusarium solani [F. solani]). Methods: Crude aqueous extracts of A. senegal and A. tortilis at 1%, 2.5% and 5% concentrations were used for screening. Antifungal activities of the extracts were evaluated against three phytopathogenic fungal strains (A. alternata, H. rostratum and F. solani) by poisoned food technique. Scanning electron microscopy (SEM) of the treated and untreated mycelia was employed to analyze the ultrastructural changes and Fourier-transform infrared (FTIR) spectrometry analysis was performed to identify important functional groups. Results: Aqueous extract of A. tortilis at high concentrations exhibited moderate inhibitory activity against the selected fungal strains. The aqueous extract of A. senegal showed no effect on A. alternata, while exhibited very mild activity against H. rostratum and F. solani at high concentrations (2.5% and 5%). Scanning electron microphotographs of the untreated fungal cells showed no structural changes (well‒defined mycelium and conidia without any distortion), whereas the treated cells showed structural distortions, twisted and wrecked mycelia and showed the presence of vesicles on the surface. FTIR analysis showed the presence of important functional groups such as alcohols, carboxylic acids and aromatic compounds. Conclusion: Results from this study indicate that the aqueous extracts of both A. senegal and A. tortilis have the potential to be used as natural fungicidal agents in the management of diseases caused by plant pathogenic fungi.

The dissociation of nuclear proteins from superhelical DNA

1978 ◽  
Vol 29 (1) ◽  
pp. 103-116
Author(s):  
J.M. Levin ◽  
E. Jost ◽  
P.R. Cook
Keyword(s):  
Molecular Weight ◽  
Free Energy ◽  
Binding Energy ◽  
Apparent Molecular Weight ◽  
Morphological Features ◽  
Nuclear Proteins ◽  
Double Labelling ◽  
Ionic Detergents ◽  
Labelling Procedure ◽  
High Concentrations

Structures retaining many of the morphological features of nuclei may be released by gently lysing human cells in solutions containing non-ionic detergents and high concentrations of salt. These nucleoids contain superhelical DNA. Using a double-labelling procedure we have compared, at different salt concentrations, the amounts and types of protein associated with human nucleoides containings superhelical or relaxed DNA. We find that the slightly lysine-rich histones (H2A and H2B) but not the arginine-rich histones (H3 and H4) dissociate more slowly from nucleoids containing superhelical DNA than from those containing relaxed DNA. A protein of apparent molecular weight of 22000 also binds more tightly to superhelical DNA. We conclude that this protein and the slightly lysine-rich histones transmute free energy of supercoiling into binding energy when they bind to superhelical DNA.

Frameworks of Transition Metals and Linkers with Two or More Functional Groups

2000 ◽  
Vol 658 ◽  
Author(s):  
Slavi C. Sevov
Keyword(s):  
Amino Acids ◽  
Transition Metals ◽  
Functional Groups ◽  
Organic Molecules ◽  
Layered Structures ◽  
Amino Groups ◽  
Effect Of Ph ◽  
Open Framework ◽  
Acidic Conditions ◽  
New Compounds

ABSTRACTHybrid inorganic/organic materials with open-framework or layered structures are known for many transition metals linked by functionalized organic molecules such as organic diphosphonates, polycarboxylates, polynitriles, etc., species with more than one equivalent functional groups. We have studied the effect of pH on such a system of cobaltmethylenediphosphonate and report three new compounds, Na3Co[(O3PCH2PO3)(OH)],Na2Co(O3PCH2PO3)•H2O, and Co2[(O3PCH2PO3)(H2O)], that form at very basic, moderately basic, and acidic conditions, respectively. More interestingstructural chemistry should be expected from linkers with two or more different functionalities. Both the carboxylic and phosphonic groups in carboxyethylphosphonic acid are used to coordinate to cobalt or calcium atoms in the new compounds Co3(O3PCH2CH2COO)2•6H2O and Ca(O3PCH2CH2COOH)•H2O. Taking one more step further in complexity we have also studied linkers with three different functional groups, phosphonated amino acids. The structures of two new compounds, Zn(O3PCH2CH(NH3)COO) and Zn(O3PCH2CH2CH(NH3)COO), are threedimensional frameworks made of zinccoordinated by both the carboxylic and phosphonic ends of the organic molecules. The amino groups are protonated and terminal in the voids of the frameworks.

NO adsorption effects on various functional molecular nanowires

2009 ◽  
Vol 47 (1) ◽  
pp. 111-120 ◽  
Author(s):  
Tien Quang Nguyen ◽  
Susan Menez Aspera ◽  
Hiroshi Nakanishi ◽  
Hideaki Kasai
Keyword(s):  
No Adsorption ◽  
Adsorption Effects

A general and practical Ni-catalyzed C–H perfluoroalkylation of (hetero)arenes

2019 ◽  
Vol 55 (47) ◽  
pp. 6723-6726 ◽  
Author(s):  
Shaoke Zhang ◽  
Nicolas Rotta-Loria ◽  
Florian Weniger ◽  
Jabor Rabeah ◽  
Helfried Neumann ◽  
...  
Keyword(s):  
Functional Groups ◽  
Free Amino ◽  
Stable Complex ◽  
Amino Groups

A direct perfluoroalkylation of (hetero)arenes using the air- and moisture-stable complex (dppf)Ni(o-tol)Cl was developed (23 examples) which allows for the synthesis of various fluorinated products and tolerates sensitive functional groups including aldehydes, free amino groups and several heterocycles.

scholarly journals Changes of the Microbial Community in Corn Soil Due to the Synergism Zeolite-Mineral Fertilizers

2016 ◽  
Vol 73 (2) ◽  
pp. 332
Author(s):  
Roxana Vidican ◽  
Vlad Stoian ◽  
Ioan Rotar ◽  
Florin Pacurar ◽  
Susana Sfechiș
Keyword(s):  
Organic Matter ◽  
Microbial Communities ◽  
Functional Groups ◽  
Growth Promotion ◽  
Radical Change ◽  
Mineral Fertilizers ◽  
Biological Crust ◽  
Microbial Functional Groups ◽  
High Concentrations ◽  
Microbial Groups

Microbial communities in agricultural ecosystems are characterized by a strong dynamic and radical change due to technological inputs applied. Corn is cultivated on large areas with high requirements for nutrients and an increased potential for activation of specific microbial groups. The aim of this study was to assess the unilateral and synergic effect of zeolite and mineral fertilizers on the development and transformation of microbial functional groups in the rhizosphere of corn. Physiological profile assessment of microbial communities has been carried out on the basis of substrate induced respiration, monitored over a period of 6 hours of incubation. The amount of CO2 registered in Microresp plates represents the activity of functional groups in decomposition of each type of substrate applied. Characteristic groups of microorganisms in maize rhizosphere are capable of decomposing acids: citric, L-malic, oxalic and α-Ketoglutaric. These substrates indicate the presence of high concentrations of organic matter in soil and the existence of a biological crust on the surface (citric acid), respectively the existence of powerful processes for the decomposition of organic material by actinomycetes (α-Ketoglutaric acid). The highest microbial activities were observed in groups of bacteria involved in processes of plant growth promotion and microbial groups with an important role in the processes of denitrification (oxalic acid). For the application of urea a triple value of activity of this type of microflora is observed. Functional groups codominant in soils cultivated with corn are specialized in efficient degradation of organic matter and biological crust, zeolite providing the complex substrate necessary for the development of these microorganisms.

Graph Based Machine Learning Interprets Diagnostic Isomer-Selective Ion-Molecule Reactions in Tandem Mass Spectrometry

2019 ◽  
Author(s):  
Jonathan A Fine ◽  
Judy Kuan-Yu Liu ◽  
Armen Beck ◽  
Kawthar Alzarieni ◽  
Xin Ma ◽  
...  
Keyword(s):  
Machine Learning ◽  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Functional Groups ◽  
Chemical Reactivity ◽  
Chemical Characterization ◽  
Training Data ◽  
Tandem Mass ◽  
Tree Model ◽  
Ion Molecule Reactions

Diagnostic ion-molecule reactions using tandem mass spectrometry can differentiate between isomeric compounds unlike a popular collision-activated dissociation methodology for the identification of previously unknown mixtures. Selected neutral reagents, such as 2-methoxypropene (MOP) are introduced into an ion trap mass spectrometer and react with protonated analytes to produce product ions diagnostic of the functional groups present in the analyte. However, the interpretation and understanding of specific reactions are challenging and time-consuming for chemical characterization. Here, we introduce a first bootstrapped decision tree model trained on 36 known ion-molecule reactions with MOP using graph-based connectivity of analyte’s functional groups as input. A Cohen Kappa statistic of 0.72 was achieved, suggesting substantial inter-model reliability on limited training data. Prospective diagnostic product predictions were made and validated for 14 previously unpublished analytes . Chemical reactivity flowcharts were introduced to understand the decisions made by the machine learning method that will be useful for chemists.<br>

Cycloisomerization of Olefins in Water

2020 ◽  
Author(s):  
Jeishla Melendez Matos ◽  
Samantha Green ◽  
Yuge Chun ◽  
Vuong Q. Dang ◽  
Russell G. Dushin ◽  
...  
Keyword(s):  
Functional Groups ◽  
Peptide Synthesis ◽  
Chemical Reactions ◽  
Catalyst Concentration ◽  
Cobalt Catalysts ◽  
Tertiary Amines ◽  
High Dilution ◽  
Reaction Efficiency ◽  
Aqueous Conditions

Preparative chemical reactions that occur efficiently under dilute, buffered, aqueous conditions in the presence of biomolecules find application in ligation, peptide synthesis, polynucleotide synthesis and sequencing. However, the identification of functional groups or reagents that are mutually reactive with one another, but unreactive with biopolymers and water, is challenging. Here we show that cobalt catalysts will react with the alkenes of unsaturated tertiary amines under dilute, aqueous, buffered conditions and promote efficient cycloisomerization, in many cases mediating a formal Friedel-Crafts reaction. We find the constraining conditions of biorthogonal chemistry to be beneficial for reaction efficiency as we obtain superior conversion at low catalyst concentration and maintain competent rates in dilute conditions. The efficiency at high dilution in the presence of buffer and nucleobases suggests that these conditions may find use on or in the presence of biomolecules.

REACTION OF FORMALDEHYDE AND THIOFORMALDEHYDE WITH MERCURIPAPAIN

1965 ◽  
Vol 43 (7) ◽  
pp. 1171-1177 ◽  
Author(s):  
W. A. Darlington ◽  
L. Keay
Keyword(s):  
Enzyme Activity ◽  
Amino Acid ◽  
Functional Groups ◽  
Tertiary Structure ◽  
Colorimetric Assay ◽  
Amino Groups ◽  
Full Activity ◽  
Amino Acid Side Chains ◽  
Lysine Residues ◽  
Secondary And Tertiary Structure

In a colorimetric assay with benzoyl-DL-arginine p-nitroanilide, acetylated and benzoylated papains retain full activity. Thus the ε-amino groups of the lysine residues are not required for enzyme activity. Intramolecular crosslinking of an enzyme could in theory stabilize secondary and tertiary structure and oppose denaturation. Thioformaldehyde is much more reactive with mercuripapain than formaldehyde, incorporating much more readily into the enzyme at equivalent concentrations. Incorporation is extensive, however, on reactive functional groups on the amino acid side chains, since acetylation decreased the incorporation markedly. In no case was there evidence of heat stabilization.

Sign in / Sign up

Export Citation Format

Share Document