Oxygen-permselectivity in new type polyorganosiloxanes with carboxyl group on the side chain

1990 ◽  
Vol 23 (6) ◽  
pp. 637-642 ◽  
Author(s):  
Manshi Ohyanagi ◽  
Hiroyuki Nishide ◽  
Koichi Suenaga ◽  
Eishun Tsuchida
Keyword(s):  
Side Chain ◽  
Carboxyl Group ◽  
New Type

ChemInform Abstract: New Type of 2-Alkyl-substituted 1,8-Naphthyridine Systems Containing a Phosphoryl Group in the Side Chain.

ChemInform ◽  
2008 ◽  
Vol 39 (34) ◽  
Author(s):  
P. S. Lemport ◽  
G. V. Bodrin ◽  
M. P. Pasechnik ◽  
A. G. Matveeva ◽  
P. V. Petrovskii ◽  
...  
Keyword(s):  
Side Chain ◽  
Phosphoryl Group ◽  
New Type

Conformation–activity relationships and the mechanism of action of penicillin

1988 ◽  
Vol 66 (11) ◽  
pp. 2733-2750 ◽  
Author(s):  
Saul Wolfe ◽  
Kiyull Yang ◽  
Maged Khalil
Keyword(s):  
Conformational Analysis ◽  
Carbonyl Group ◽  
Active Site ◽  
Global Minimum ◽  
Peptide Bond ◽  
Biologically Active ◽  
Penicillin G ◽  
Side Chain ◽  
Geometrical Parameters ◽  
Carboxyl Group

Using the MMPEN parameters of Allinger's MMP2(85) force field, a conformational analysis has been performed on four biologically active penicillins; D-ampicillin, L-α-phenoxyethylpenicillin, penicillin G, and penicillin V, and on five biologically inactive or much less active penicillins: L-ampicillin, D-α-phenoxyethylpenicillin, N-methylpenicillin G, 6α-methylpenicillin G, and bisnorpenicillin G. Antibacterial activity is found to be associated with the existence of a global minimum having a compact structure, whose convex face is accessible to a penicillin binding protein (PBP), with the C3-carboxyl group and the side-chain N-H exposed on this face. Using the MMPEP parameters of MMP2(85), a conformational analysis has been performed on phenylacetyl-D-Ala-D-Ala-O−, a peptide model of the normal substrate of a PBP. Labischinski's global minimum has been reproduced, along with structures that correspond to Tipper and Strominger's proposal that the N4—C7 bond of a penicillin corresponds to the Ala–Ala peptide bond, and to Hasan's proposal that the N4—C5 bond of penicillin corresponds to the peptide bond. For both models, conformations of the peptide related to the pseudoaxial and pseudoequatorial conformations of the thiazolidine ring of penicillin G have been examined. It is concluded that penicillin is not a structural analog of the global minimum of the peptide; however, comparisons based on unbound conformations of PBP substrates are unable to determine which model is more appropriate, or which conformation of penicillin G is the biologically significant one. Using the ECEPP/MMPEP strategy, a model of the active site of a PBP has been obtained, following a search of 200,000 structures of the peptide Ac-NH-Val-Gly-Ser-Val-Thr-Lys-NH-Me. This peptide contains the sequence at the active site of a PBP of Streptomyces R61, for which it is also known that the C3-carboxyl group of penicillin binds to the ε-amino group of lysine, and the β-lactam reacts chemically with the serine OH. The lysine and serine side chains and the C-terminal carbonyl group are found to occupy the concave face of the active site model.A strategy for the docking of penicillins or peptides to this model, with full minimization of the conformational energies of the complexes, has been devised. All active penicillins bind through strong hydrogen bonds to the C3-carboxyl group and the side-chain N-H, and with a four-centered relationship between the O-H of serine and the (O)C-N of the β-lactam ring. The geometrical parameters of this relationship are reminiscent of those found in the gas phase transition state of neutral hydration of a carbonyl group. When the energies of formation and geometries of the pseudoaxial and pseudoequatorial penicillin G complexes are examined, there is now a clear preference for the binding of the pseudoaxial conformation, which is the global minimum of the uncomplexed penicillin in this case. A similar examination of the peptide complexes reveals that only the conformation of the peptide that corresponds to Tipper and Strominger's model, and is based on the pseudoaxial conformation of penicillin G, can form a complex with a geometry and energy comparable to those of a biologically active penicillin.

scholarly journals NMR and X-ray studies of apetalic acid isolated from Calophyllum brasiliense and of its chiral amides

2021 ◽  
Author(s):  
Marie-Rose Van Calsteren ◽  
Ricardo Reyes-Chilpa ◽  
Chistopher K Jankowski ◽  
Fleur Gagnon ◽  
Simón Hernández-Ortega ◽  
...  
Keyword(s):  
Antimycobacterial Activity ◽  
Side Chain ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Rain Forests ◽  
X Ray ◽  
X Ray Crystallography ◽  
Calophyllum Brasiliense ◽  
Derivatives Of

The tropical tree Calophyllum brasiliense (Clusiaceae) grows in the rain forests from Brazil to Mexico. Its leaves, as well as those of other Calophyllum species, are rich sources of chromanone acids, such as apetalic acid, isoapetalic acid, and their derivatives. Apetalic acid has shown significant antimycobacterial activity. The biological activity of apetalic acid has been related to the configuration of three asymmetric centers and the stereochemistry of the molecule; however, the C-19 configuration in the acidic side chain has not been fully resolved. For this reason, the unequivocal determination of the absolute configuration by means of X-ray crystallography in a sample of unique homogeneous apetalic acid stereoisomer was the most important point to start this study. We prepared some chiral amides using the carboxyl group. We determined the C-19 stereochemistry of apetalic acid, and its specific chiral derivatives, using NMR, X-ray diffraction methods, and molecular mechanics. Finally, we observed that steric hindrance in the side chain of apetalic acid leads to restriction of rotation around the pivotal link C-10 and C-19 establishing chiral centers at C2(R), C3(S), and C19(R). We were able to separate derivatives of these two high-rotatory-barrier conformers of apetalic acid by forming diastereoisomeric amides with phenylglycine methyl ester having a chiral center at C-2’. Our results allowed the conclusion of the existence of atropisomerism in the apetalic acid molecule.

scholarly journals Preparation of side chain liquid crystal polyether chelating resin and its adsorption properties for Cu2+ in water

2021 ◽  
Author(s):  
Chaoyi Qian ◽  
Meng Li ◽  
Shuang Wang ◽  
Qing Gao ◽  
Huaiwei Yao ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Influence Factors ◽  
Chelating Resin ◽  
Side Chain ◽  
Order Kinetic ◽  
Adsorption Model ◽  
Order Kinetic Model ◽  
Group A ◽  
New Type ◽  
Cationic Ring Opening Polymerization

Abstract With epoxycyclohexane as critical modifying monomer, the copolyether was obtained by cationic ring-opening polymerization of epichlorohydrin and epoxycyclohexane. Then biphenyl was used as the mesogen, and diglycolamidic acid was used as the terminal chelating group, a new type of side chain liquid crystal polyether chelating resin was prepared at last. The adsorption influence factors, reuse performance, adsorption model and adsorption kinetics of the chelated resin on Cu 2+ in water were studied systematically. The results showed that the resin has good adsorption and reuse performance for the treatment of Cu 2+ in water, and the adsorption of Cu 2+ is Langmuir monolayer adsorption, and the adsorption process conforms to a quasi-second-order kinetic model. The adsorption performances of the chelated resin has great potential for recovery of copper resource from non-ferrous smelting industry.

Effect of certain thyroxine analogues on liver cholesterol

1960 ◽  
Vol 199 (6) ◽  
pp. 1000-1002 ◽  
Author(s):  
Maurice M. Best ◽  
Charles H. Duncan
Keyword(s):  
Butyric Acid ◽  
Liver Cholesterol ◽  
Side Chain ◽  
Carboxyl Group ◽  
Degree Of Dissociation ◽  
Cholesterol Levels

l-Thyroxine, l-triiodothyronine, their d-isomers, and their formic, acetic, propionic and butyric acid analogues were given to cholesterol-thiouracil-fed rats and the effect on thyroid weight and serum and liver cholesterol determined. l-Thyroxine, d-thyroxine and tetraiodothyroformic acid were also given to cholesterol-fed rats and the effect on oxygen use and serum and liver cholesterol measured. The substitution of either d-alanine or a carboxyl group for the l-alanine side chain of thyroxine and triiodothyronine resulted in a degree of dissociation of goiter-inhibiting and liver cholesterol effects. Thus, these substituted compounds at doses having equal or less goiter-inhibiting effects resulted in significantly lower liver cholesterol levels than did l-thyroxine or l-triiodothyronine. The effect of d-thyroxine and tetraiodothyroformic acid on liver cholesterol was also disproportionate to their calorigenic activity as compared to l-thyroxine.

Bacteriochlorophyll e : structure and stereochemistry of a new type of chlorophyll from Chlorobiaceae

1976 ◽  
Vol 273 (924) ◽  
pp. 277-285 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Oxidative Degradation ◽  
Chemical Properties ◽  
Structural Formula ◽  
Side Chain ◽  
Physical And Chemical Properties ◽  
New Type ◽  
Physical And Chemical ◽  
Bacteriochlorophyll E ◽  
And Chemical Properties

A so far unknown chlorophyll has been isolated from several strains of brown-coloured chlorobacteria and has been designated bacteriochlorophyll e . Comparison of the physical and chemical properties of the new chlorophyll with those of bacteriochlorophylls c and d ( Chlorbium chlorophylls) allows one to deduce its structural formula. The stereochemistry of the hydroxyethyl side chain of bacteriochlorophylls c, d and e can be determined by a modified Horeau analysis of these pigments, and the results thus obtained are in agreement with those derived from oxidative degradation experiments. The latter method allows one furthermore to prove the structure of bacteriochlorophylls c and d proposed by Holt, and to establish the absolute configuration at carbon atoms 7 and 8. The presence of a δ-methylsubstituent in bacteriochlorophylls c and e is unambiguously demonstrated by nuclear magnetic resonance.

Azoverdin -an Isopyoverdin

1996 ◽  
Vol 51 (11-12) ◽  
pp. 772-780 ◽  
Author(s):  
R Michalke ◽  
K Taraz ◽  
H Budzikiewiez
Keyword(s):  
Carboxylic Acid ◽  
Succinic Acid ◽  
Peptide Chain ◽  
Side Chain ◽  
Carboxyl Group ◽  
Amino Group ◽  
Present Evidence ◽  
N Terminus

For azoverdin, the siderophore of Azomonas macrocytogenes ATCC 12334, a pyoverdintype structure has been suggested. We now present evidence that it is actually an isopyoverdin. Also the sequence of the peptide chain has to be revised. Azoverdin comprises, therefore, the chromophore (3S)-5-amino-1,2-dihydro-8,9-dihydroxy-3H -pyrimido[1,2a]quinoline- 3-carboxylic acid whose amino group is bound to a succinamide residue while the carboxyl group is attached to the N -terminus of L-Hse-[2-(R-1-amino-3-hydroxypropyl)-3,4,5,6- tetrahydropyrimidine-65-carboxylic acid]-N5-acetyl-N5,-hydroxy-ᴅ-Orn-ᴅ-Ser-N5-acetyl-N5- hydroxy-ʟ-Orn. In addition to azoverdin congeners with succinic acid (azoverdin A ) and with ʟ-Glu (azoverdin G ), resp., instead of the succinamide side chain could be isolated.

New type of 2-alkyl-substituted 1,8-naphthyridine systems containing a phosphoryl group in the side chain

2007 ◽  
Vol 56 (9) ◽  
pp. 1911-1917 ◽  
Author(s):  
P. S. Lemport ◽  
G. V. Bodrin ◽  
M. P. Pasechnik ◽  
A. G. Matveeva ◽  
P. V. Petrovskii ◽  
...  
Keyword(s):  
Side Chain ◽  
Phosphoryl Group ◽  
New Type

scholarly journals The hydrogen ion equilibria of horseradish peroxidase and apoperoxidase

1971 ◽  
Vol 124 (3) ◽  
pp. 605-614 ◽  
Author(s):  
C Phelps ◽  
L Forlani ◽  
E Antonini
Keyword(s):  
Horseradish Peroxidase ◽  
Potassium Chloride ◽  
Hydrogen Ion ◽  
Side Chain ◽  
Carboxyl Group ◽  
Tyrosine Residue ◽  
Guanidinium Chloride ◽  
Spectroscopic Investigations ◽  
Imidazole Group ◽  
Proton Dissociation

1. The reversible proton dissociation equilibria of peroxidase, apoperoxidase and haem-recombined apoperoxidase have been explored in 150mm-potassium chloride at 20°C at pH3–11.5. 2. Complementary heat measurements have been made of the classes of titratable groups to determine their intrinsic ΔH dissociation. 3. These curves are interpreted as showing that there are two histidine residues capable of titration in peroxidase whereas there are three such in apoperoxidase. 4. Concomitant spectroscopic investigations indicate profound differences in the tyrosine ionizations in the two proteins. In peroxidase one group only of the five residues ionizes up to pH11.5. In apoperoxidase four residues are titratable. 5. Spectroscopic titration in 6m-guanidinium chloride and 150mm-potassium chloride reveal one tyrosine residue fewer in peroxidase than in apoperoxidase. 6. These findings are discussed in terms of the ‘side chain’ groups responsible for binding the haem group in peroxidase. A proximal imidazole group seems probable as is also the involvement of a distally placed tyrosine. 7. The differences between apo- and holo-peroxidase are stressed, particularly in respect of abnormal carboxyl group titration in the former.

scholarly journals ANTIGEN RECOGNITION AND THE IMMUNE RESPONSE

1972 ◽  
Vol 136 (2) ◽  
pp. 387-391 ◽  
Author(s):  
Sefik S. Alkan ◽  
Maurice E. Bush ◽  
Danute E. Nitecki ◽  
Joel W. Goodman
Keyword(s):  
Immune Response ◽  
Hydroxyl Group ◽  
Side Chain ◽  
Low Molecular Weight ◽  
Carboxyl Group ◽  
Amino Group ◽  
Structural Requirements ◽  
Phenolic Ring ◽  
Cellular Immune ◽  
Charged Group

The low molecular weight compound L-tyrosine-azobenzenearsonate (RAT) induces a cellular immune response in guinea pigs. The contribution of the side chain of tyrosine to the immunogenicity of RAT and the structural requirements at that position for immunogenicity were assessed by synthesizing a series of analogs of RAT containing modifications in the side chain of tyrosine and employing them as immunogens. Removal of either the carboxyl or amino group did not markedly affect immunogenicity, measured by the induction of delayed cutaneous sensitivity, whereas deletion of both completely abolished it. However, a charged group was not required since side chains containing a polar hydroxyl group could substitute for chains bearing an amino or carboxyl group. The size of the side chain exerted a pronounced influence; the charged or polar substituent had to be extended from the phenolic ring by at least two carbon atoms in order to confer immunogenicity.

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