Racemization rates of 3,4-didehydro-2-amino acids

1989 ◽  
Vol 54 (12) ◽  
pp. 3381-3386 ◽  
Author(s):  
Libor Havlíček ◽  
Jan Hanuš ◽  
Jan Němeček
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Acidic Medium

The racemization rates of amino acids in acidic medium (acetic acid) were studied. The sensitivity to racemization decreases in the order (E)-3,4-didehydroornithine > (E)-Nδ-Z-3,4-didehydroornithine >> (Z)-3,4-didehydronorvaline > ornithine, norvaline. (E)-3,4-Didehydroornithine is also relatively rapidly racemized on heating with 5 M or 0.05 M-HCl (100 °C).

Solid Phase Synthesis of a Somatostatin Amide Analogue Using Acid Labile t-Bumeoc Protection and an Acid Labile Anchor Group

1992 ◽  
Vol 57 (8) ◽  
pp. 1707-1718
Author(s):  
Wolfgang Voelter ◽  
Gerhard Breipohl ◽  
Chryssa Tzougraki ◽  
Eveline Jungfleisch-Turgut
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Somatostatin Analogue ◽  
Phase Synthesis ◽  
Anchor Group ◽  
Amide Form ◽  
Polystyrene Resin ◽  
Acid Labile

The solid phase synthesis of an amidated somatostatin analogue based on the principle of differentiated acidolysis is described. The acid labile and smoothly cleavable t-Bumeoc moiety (1% TFA/DCM) is used for temporary Nα-protection of D- and L-amino acids and [4-[[[9H-fluoren-9-yl-methoxycarbonyl]amino](4-methoxyphenyl)methyl]-2-methylphenoxy]acetic acid, attached to an aminomethylated polystyrene resin is used as acid sensitive linker of the solid carrier which releases the peptide in its amide form by treatment with TFA. Its preparation is described in detail.

Hydrogen Peroxide Might Bleach Natural Dentin by Oxidizing Phosphoprotein

2018 ◽  
Vol 97 (12) ◽  
pp. 1339-1345 ◽  
Author(s):  
T. Jiang ◽  
Y.R. Guo ◽  
X.W. Feng ◽  
Y. Sa ◽  
X. Yang ◽  
...  
Keyword(s):  
Amino Acids ◽  
Hydrogen Peroxide ◽  
Acetic Acid ◽  
Aromatic Amino Acids ◽  
Disodium Salt ◽  
Tooth Bleaching ◽  
Distilled Water ◽  
Fluorescent Properties ◽  
Fluorescent Intensity ◽  
Tooth Color

Recent studies suggested that bleaching agents may whiten teeth by oxidizing the fluorescent materials, which are the proteins located in the organic-inorganic interface. Therefore, we postulated that fluorescence of dentin came from dentin phosphoprotein (DPP) and that bleaching agents might bleach dentin by oxidizing DPP. Fifty-six specimens were randomly divided into 4 groups and exposed to distilled water, hydrogen peroxide (HP), ethylenediamine tetraacetic acid disodium salt (EDTA), and acetic acid for 24 h. After measuring the organic and inorganic components, fluorescence, and color characteristics of dentin before and after exposure, we found that when DPP was removed from dentin by EDTA, fluorescent intensity declined proportionally with the reduction in Raman relative intensity, and dentin was whitened considerably, with an Δ E value 6 times higher than that of the distilled water group. On the contrary, due to the incapability of acetic acid to dissolve DPP during decalcification, fluorescent intensity values and tooth color remained nearly unchanged after exposure to acetic acid. Dentin exposed to neutral HP showed no obvious morphologic and organic/inorganic component changes except for the destruction of DPP. Similarly, dramatically decreased fluorescent intensity and lightened color were found in the HP group. Moreover, DPP solution of the HP group exhibited decreased ultraviolet absorbance, especially between 250 and 300 nm, which arose from aromatic amino acids. The results indicated that DPP was responsible for the fluorescent properties of dentin and that HP might bleach dentin by the oxidization of aromatic amino acids in DPP. These findings are of great significance in promoting our further understanding of the mechanism of tooth bleaching and the fluorescent property of normal dentin.

scholarly journals A method for the separation of peptides and α-amino acids

1968 ◽  
Vol 107 (3) ◽  
pp. 335-340 ◽  
Author(s):  
D. K. J. Tommel ◽  
J. F. G. Vliegenthart ◽  
T. J. Penders ◽  
J F Arens
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Acetate Buffer ◽  
Acid Fraction ◽  
Peptide Fraction ◽  
Acidic Peptide ◽  
Peptide Fractions ◽  
Acetate Form

1. Peptides and α-amino acids, occurring in mixtures from various sources, can be separated into one fraction containing the amino acids and several peptide fractions. This is achieved by chelation of the mixture with Cu2+ ions and subsequent chromatography of these chelates over the acetate form of diethylaminoethylcellulose or triethylaminoethylcellulose. 2. The amino acid fraction is obtained by elution with 0·01m-collidine–acetate buffer, pH8·0. 3. Peptide fractions are eluted with 0·01m-collidine–acetate buffer, pH4·5, 0·17n-acetic acid and 0·1n-hydrochloric acid respectively. 4. With the exception of aspartic acid and glutamic acid, which are partly found in the acidic peptide fraction, the amino acids are completely separated from the peptides. 5. Contamination of the acidic peptide fraction with glutamic acid and aspartic acid can be largely avoided by previous addition of an excess of arginine. 6. Copper is removed from the eluates by extraction with 8-hydroxyquinoline in chloroform.

On-Chip Indirect Detection of Non-Fluorescent Analytes Using Fluorescent Spacers

2007 ◽  
Author(s):  
Tarun K. Khurana ◽  
Juan G. Santiago
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Lower Bound ◽  
Organic Acids ◽  
Indirect Detection ◽  
Phenylpropionic Acid ◽  
Initial Concentration ◽  
On Chip

We present a technique that accomplishes on-chip preconcentration, separation and indirect detection of nonfluorescent analytes by leveraging isotachophoresis (ITP) and a set of fluorescent species termed spacers. The non-fluorescent analyte zones are detected as dark zones/gaps between fluorescent spacer zones. The length of this gap quantifies the initial concentration of the non-fluorescent analyte and mobilities of the fluorescent spacers on either side provide the upper and lower bound for the analyte mobility. We have successfully demonstrated separation and detection of amino acids, serine and phenylalanine, as well as other organic acids, acetic acid and phenylpropionic acid with this technique. Using three fluorescent spacers, we were able to detect ∼10 μM concentration of non-fluorescent analytes.

Amino group requirement for in vitro intestinal transport of amino acids

1962 ◽  
Vol 202 (1) ◽  
pp. 171-173 ◽  
Author(s):  
Richard P. Spencer ◽  
Ted M. Bow ◽  
Mary Anne Markulis
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Cinnamic Acid ◽  
Concentration Gradient ◽  
Anthranilic Acid ◽  
Intestinal Transport ◽  
Amino Group ◽  
Phenylpyruvic Acid ◽  
Phenyllactic Acid

The amino group requirement for transintestinal transport of amino acids against a concentration gradient was investigated using hamster everted intestinal sacs. Although glycine (5 x 10–3 m) was transported against a concentration gradient, acetic acid was not. Similarly, l-phenylalanine was transported, whereas phenylpyruvic acid, phenylpropionic acid, phenyllactic acid, and cinnamic acid were not. l-Tryptophan was transported, but indolyllactic acid was not. The amino group was thus essential for transport by this system. n-Methylglycine and l-proline were accumulated from mucosa to serosa against a concentration gradient. Hence, one hydrogen of the amino group can be replaced. However, n-phenylglycine was not accumulated across these preparations, suggesting that the moiety replacing the amino hydrogen can not be sterically bulky. α-l-Alanine was transported against a concentration gradient from mucosa to serosa, but ß-alanine was not. This is in contrast to other systems which accumulate ß-alanine against a concentration gradient. Anthranilic acid, with the amino group in a relative ß position, was also not accumulated across everted intestinal sacs.

Phosphate Production and Analysis in the Non-Enzymatic Activation of Amino Acids by ATP when Using Hydroxylamine as a Trapping Agent

1981 ◽  
Vol 36 (6) ◽  
pp. 732-734 ◽  
Author(s):  
Dail W. Mullins ◽  
James C. Lacey
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Inorganic Phosphate ◽  
Hydroxamic Acids ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Chromatography Method ◽  
Total Inhibition ◽  
Enzymatic Activation ◽  
Trapping Agent

Abstract Phosphate Production, Hydroxylamine, ATP Saygin and Decker [6, 7] have reported that the formation of hydroxamic acids in solutions containing ATP, MgCl2, hydroxylamine and an acidic acceptor (acetic acid or amino acids) is not accompanied by the release of inorganic phosphate from ATP. Using an ion exchange chromatography method developed by Lowenstein [8] to separate the various components of such reaction mixtures, we now show that inorganic phosphate, as well as some pyrophosphate, is produced during incubation at 50 °C. Evidence is also presented to indicate that the failure of Saygin and Decker [6, 7] to detect phosphate is due to a total inhibition of their phosphate assay system by ATP.

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