Dissociation constants of host–guest complexes of alkyl-bearing compounds with β-cyclodextrin and "hydroxypropyl-β-cyclodextrin"

1996 ◽  
Vol 74 (5) ◽  
pp. 736-744 ◽  
Author(s):  
Oswald S. Tee ◽  
Timothy A. Gadosy ◽  
Javier B. Giorgi
Keyword(s):  
Amino Acids ◽  
Key Words ◽  
Dissociation Constants ◽  
Hydroxyl Groups ◽  
Strong Correlations ◽  
Inhibition Kinetics ◽  
Displacement Method ◽  
Alkyl Derivatives ◽  
Unit Slope ◽  
A Chain

Dissociation constants (Kd) of host–guest complexes formed from β-cyclodextrin or "hydroxypropyl-β-cyclodextrin" (β-CD and Hp-β-CD) and several types of aliphatic guests (alcohols, alkanesulfonate ions, alkylamines, and α-amino acids), with up to eight carbons in a chain, are reported. These constants were determined by inhibition kinetics and by a spectrofluorometric displacement method based on competition with 1-anilino-8-naphthalenesulfonate ion as a fluorescent probe. The value of Kd for a particular amine is close to that for the corresponding alcohol. For linear alkyl derivatives, there are strong correlations between pKd (= −log Kd) and the chain length of the guest, with slopes around 0.5, complementing trends that were noted earlier. Furthermore, the strengths of binding of various aliphatic derivatives to β-CD and to Hp-β-CD are close, with Kd values for the two CDs usually being within a factor of 2 of each other. Overall, for the binding of over 50 alkyl-bearing derivatives, there is a good correlation of pKd for Hp-β-CD with that for β-CD, with unit slope. These observations imply that the binding of simple aliphatic guests to Hp-β-CD is not greatly influenced by the modification of the hydroxyl groups on the primary side of the β-CD cavity but this may not be true for longer aliphatic derivatives (>C8) or for aromatics that penetrate farther into the CD cavity. Key words: cyclodextrins, host–guest complexes, dissociation constants.

DEGRADATION OF MELANOIDINS BY SOIL MICROORGANISMS UNDER LABORATORY CONDITIONS

1987 ◽  
Vol 67 (2) ◽  
pp. 409-414 ◽  
Author(s):  
KARL C. IVARSON ◽  
LAURE M. BENZING-PURDIE
Keyword(s):  
Amino Acids ◽  
Key Words ◽  
Soil Microorganisms ◽  
Soil Microbes ◽  
C:N Ratio ◽  
Soil Suspension ◽  
Penicillium Species ◽  
Laboratory Conditions

Synthetic melanoidins, unlabeled and U–14C labeled, mixed with sand, inoculated with a soil suspension and incubated in Warburg vessels for 30 d, decomposed slowly. Reactants (amino acids, sugars and NH4 salts) involved in melanoidin formation had no influence on rate of degradation, nor did the pH at which the melanoidins were synthesized. However, temperature of synthesis affected the rate; an increase led to a decrease in biodegradability paralleled by both increase in C:N ratio and unsaturation. At lower temperatures species of Penicillium, Cladosporium and Paecilomyces were the dominant fungi degrading the polymers, while at higher temperatures only Penicillium species were present. Key words: Melanoidins, decomposition by soil microbes

Coupling of Steroid O-(Carboxymethyl)oxime Derivatives with Amino Alcohols

1996 ◽  
Vol 61 (2) ◽  
pp. 288-297 ◽  
Author(s):  
Vladimír Pouzar ◽  
Ivan Černý
Keyword(s):  
Amino Acids ◽  
Hydroxy Group ◽  
Building Blocks ◽  
Amino Alcohols ◽  
New Approach ◽  
Alternative Synthesis ◽  
Oxime Derivatives ◽  
A Chain ◽  
Derivatives Of

New approach to the preparation of steroids with connecting bridge, based on an O-carboxymethyloxime (CMO) structure, and with terminal hydroxy group, is presented. 17-CMO derivatives of 3β-acetoxy- and 3β-methoxymethoxyandrost-5-en-17-one were condensed with α,ω-amino alcohols to give derivatives with a chain of seven to nine atoms. After THP-protection, these compounds were converted to 3-keto-4-ene derivatives. An alternative synthesis consisted in transformation of 17-CMO derivatives with bonded amino acids by reduction of the terminal carboxyl. The resulting compounds were designed as building blocks for the preparation of bis-haptens for sandwich immunoassays.

Crystal structure of rivastigmine hydrogen tartrate Form I (Exelon®), C14H23N2O2(C4H5O6)

2016 ◽  
Vol 31 (2) ◽  
pp. 97-103 ◽  
Author(s):  
James A. Kaduk ◽  
Kai Zhong ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Carbonyl Oxygen ◽  
Strong Hydrogen Bond ◽  
Hydroxyl Groups ◽  
A Chain ◽  
Tartrate Anion

The crystal structure of rivastigmine hydrogen tartrate has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Rivastigmine hydrogen tartrate crystallizes in space group P21 (#4) with a = 17.538 34(5), b = 8.326 89(2), c = 7.261 11(2) Å, β = 98.7999(2)°, V = 1047.929(4) Å3, and Z = 2. The un-ionized end of the hydrogen tartrate anions forms a very strong hydrogen bond with the ionized end of another anion to form a chain. The ammonium group of the rivastigmine cation forms a strong discrete hydrogen bond with the carbonyl oxygen atom of the un-ionized end of the tartrate anion. These hydrogen bonds form a corrugated network in the bc-plane. Both hydroxyl groups of the tartrate anion form intramolecular O–H⋯O hydrogen bonds. Several C–H⋯O hydrogen bonds appear to contribute to the crystal energy. The powder pattern is included in the Powder Diffraction File™ as entry 00-064-1501.

scholarly journals Localization of sites through which C-reactive protein binds and activates complement to residues 14-26 and 76-92 of the human C1q A chain.

1992 ◽  
Vol 175 (5) ◽  
pp. 1373-1379 ◽  
Author(s):  
H Jiang ◽  
F A Robey ◽  
H Gewurz
Keyword(s):  
Amino Acids ◽  
Binding Site ◽  
Immunoglobulin G ◽  
Inhibitory Activity ◽  
Sequence Specificity ◽  
C Reactive Protein ◽  
Reactive Protein ◽  
Binding Regions ◽  
A Chain ◽  
A Charge

Studies were initiated to localize the C-reactive protein (CRP) binding site on the collagen-like region (CLR) of C1q. CRP bound preferentially to the A chain of reduced C1q, in contrast to aggregated immunoglobulin G (Agg-IgG), which reacted preferentially with the C chain. A group of C1q A chain peptides, including peptides identical to residues 81-97, 76-92, and 14-26, respectively, were synthesized from predicted binding regions. Peptide 76-92 contained two proximal lysine groups, and peptide 14-26 contained four proximal arginine groups. CRP-trimers and CRP-ligand complexes did not bind to immobilized peptide 81-97, but bound avidly to immobilized peptides 76-92 and 14-26. Agg-IgG did not bind to any of the peptides. Peptide 76-92 partially, and peptide 14-26 completely, inhibited binding of CRP to intact C1q. Peptide 14-26 also blocked C consumption initiated by CRP, but not by IgG. Replacement of the two prolines with alanines, or scrambling the order of the amino acids, resulted in loss of ability of peptide 14-26 to inhibit C1q binding and C activation by CRP, indicating a sequence specificity, and not a charge specificity alone, as the basis for the inhibitory activity of the peptide. Similar investigations with scrambled peptides showed a sequence specificity for the effects of peptide 76-92 as well. DNA and heparin inhibited binding of CRP trimers to intact C1q, as well as to each peptide 14-26 and 76-92, suggesting involvement of these regions in C1q-CLR binding reactions generally. Collectively, these data identify two cationic regions within residues 14-26 and 76-92 of the C1q A chain CLR as sites through which CRP binds and activates the classical C pathway, and suggest that these residues represent significant regions for C1q CLR binding reactions generally. To our knowledge, this represents the first delineation of sites on C1q through which binding and activation of the classical C pathway can occur.

scholarly journals The affinity constants of amphoteric electrolytes. III.—Methylated amino-acids

1906 ◽  
Vol 78 (522) ◽  
pp. 140-149
Keyword(s):  
Aqueous Solution ◽  
Amino Acids ◽  
Ammonium Hydroxide ◽  
Ammonia Solution ◽  
Present Communication ◽  
Equilibrium Equations ◽  
Hydrated Form ◽  
Affinity Constants ◽  
Alkyl Derivatives

The main object of the present communication is to discuss the results obtained by Johnston and Cumming in their investigation of the affinity constants of methylated amino-acids. Before entering on the discussion of these amphoteric electrolytes, however, it is necessary to refer to certain general principles applicable to the affinity constants of simple electrolytes, in particular of simple bases. Amino-bases and their alkyl derivatives are supposed to exist in aqueous solution to a greater or less degree in the hydrated form, and it is this hydrated form winch we conceive to give rise to the characteristic ion OH' of soluble bases. Thus the alkalinity of ammonia solution is attributed primarily to the ionisation of ammonium hydroxide, according to the equilibrium equations NH 3 +H 2 O⇄NH 4 OH⇄NH 4 +OH'.

Chelating polymers. I. The synthesis and acid dissociation behavior of several N-(p-vinylbenzenesulfonyl)-substituted diaminopolyacetic acid monomers, monomeric analogues, and related intermediates

1970 ◽  
Vol 48 (1) ◽  
pp. 163-175 ◽  
Author(s):  
R. M. Genik-Sas-Berezowsky ◽  
I. H. Spinner
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Inductive Effects ◽  
Cyclic Amide ◽  
Amino Acid Analogues ◽  
Related Compounds ◽  
Chelating Polymers ◽  
Made In

Two new chelating monomers, N-(p-vinylbenzenesulfonyl)1,2-diaminoethane-N′,N′-diacetic (SS-EDDA) and -N,N′,N′-triacetic (SS-ED3A) acids, as well as several monomeric analogues and related intermediates have been prepared. In addition, 2-oxo-1-piperazine acetic (S-KP), 3-oxo-1-piperazine acetic (U-KP), and 2-oxo-1,4-piperazine diacetic (3-KP) acids have been synthesized and the interconvertibility between these cyclic amides and their unsubstituted linear amino acid analogues, ethylene-diamine-N,N′-diacetic (S-EDDA), -N,N-diacetic (U-EDDA), and -N,N,N′-triacetic (ED3A) acids respectively, was demonstrated.The acid dissociation constants of the various amino acids were determined potentiometrically at 25° and μ = 0.1 M(KNO3) and the results were compared with the hydrogen ion affinities of related compounds. Dissociation schemes were proposed for all the compounds based on these results. Rationalizations of the linear amino acid and the cyclic amide dissociation constants were made in terms of the effects of cyclization and the inductive effects of neighboring groups. These rationalizations were found to be helpful in clarifying the dissociation schemes previously proposed for several of the linear amino acids.

The effect of oligosaccharides and lactitol on the ileal digestibilities of amino acids, monosaccharides and bacterial populations and metabolites in the small intestine of weanling pigs

1995 ◽  
Vol 75 (1) ◽  
pp. 99-107 ◽  
Author(s):  
V. M. Gabert ◽  
W. C. Sauer ◽  
R. Mosenthin ◽  
M. Schmitz ◽  
F. Ahrens
Keyword(s):  
Amino Acids ◽  
Small Intestine ◽  
Key Words ◽  
Soybean Meal ◽  
Corn Starch ◽  
Period Change ◽  
Distal Ileum ◽  
Weanling Pigs ◽  
Bacterial Populations ◽  
Nutrient Digestion

An experiment was carried out to examine the effects of supplementing diets for weanling pigs with oligosaccharides and LAC on nutrient digestion and bacterial populations and metabolites in the small intestine. Twelve barrows, weaned at 28 d, were fitted with a simple T-cannula at the distal ileum. The BW of the pigs at weaning and at the conclusion of the experiment were 9.1 and 13.8 kg, respectively. The pigs were fed four diets based on barley, wheat and soybean meal according to a two-period change-over design. The diets were formulated to contain 18% CP. Transgalactosylated oligosaccharides (0.2%), GUO (0.2%) and LAC (1%, 4-O-β-D-galactopyranosyl-D-sorbitol) were included at the expense of corn starch. Supplementation with oligosaccharides or LAC had little effect on the apparent ileal digestibilities of AA and monosaccharides. Supplementation of diets with oligosaccharides or LAC did not affect (P > 0.05) the monosaccharide concentrations in ileal digesta except for galactose which was higher (P < 0.05) in digesta from pigs fed the diet supplemented with LAC. The daily ileal output of monosaccharides, pH, ammonia and VFA concentrations, bacterial populations in ileal digesta and incidence of diarrhea were not affected (P > 0.05). Therefore, the supplementation of diets for weanling pigs (9.1–13.8 kg) with oligosaccharides or LAC at these levels does not affect nutrient digestibilities and bacterial populations in the small intestine. Key words: Pigs, oligosaccharides, lactitol, digestibility, bacteria

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