Dipeptide Glycyl Research Articles

Synthesis of glycyl-(<i>S</i>)-5-hydroxynorvaline

The dipeptide glycyl-( S )-5-hydroxynorvaline was obtained from 1- tert -butyl 5-methyl N -Boc-glycyl-( S )-glutamate as a result of saponification and subsequent reduction of the activated 5-carboxyl group with sodium borohydride followed by removal of the N -Boc and OBu t protecting groups by refluxing in a dioxane-water mixture. Using the example of the synthesis of ( S )-5-hydroxynorvaline, it has been shown that the used sequence of chemical transformations is not accompanied by racemization.

Fluorescent and Photosensitizing Conjugates of Cell-Penetrating Peptide TAT(47-57): Design, Microwave-Assisted Synthesis at 60 °C, and Properties.

Conjugates based on cell-penetrating peptides (CPPs) are scientifically relevant owing to their structural complexity; their ability to enter cells and deliver drugs, labels, antioxidants, bioactive compounds, or DNA fragments; and, consequently, their potential for application in research and biomedicine. In this study, carboxyamidated fluorescently labeled conjugates FAM-GG-TAT(47-57)-NH2 and FAM-PEG6-TAT(47-57)-NH2 and photosensitizer-labeled conjugate Chk-PEG6-TAT(47-57)-NH2 [where TAT(47-57) is the CPP, 5(6)-carboxyfluorescein is the (FAM) fluorophore, chlorin k (Chk) is the photosensitizer, and the dipeptide glycyl–glycine (GG) or hexaethylene glycol (PEG6) is the spacer] were originally designed, prepared, and fully characterized. Practically, all chemical reactions of the synthetic steps (peptide synthesis, spacer incorporation, and conjugation) were microwave-assisted at 60 °C using optimized protocols to give satisfying yields and high-quality products. Detailed analyses of the conjugates using spectrofluorimetry and singlet oxygen detection showed that they display photophysical properties typical of FAM or Chk. Anticandidal activity assays showed that not only this basic property of TAT(47-57) was preserved in the conjugates but also that the minimal inhibitory concentration was slightly reduced for cells incubated with PS-bearing conjugate Chk-PEG6-TAT(47-57)-NH2. Overall, these results indicated that the synthetic approach on-resin assisted by microwaves at 60 °C is simple, straightforward, selective, metal-free, sufficiently fast, cleaner, and more cost-effective than those previously used for preparing this type of macromolecule. Furthermore, such new data show that microwaves at 60 °C and/or conjugation did not harm the integrity of the conjugates’ constituents. Therefore, FAM-GG-TAT(47-57)-NH2, FAM-PEG6-TAT(47-57)-NH2, and Chk-PEG6-TAT(47-57)-NH2 have high potential for practical applications in biochemistry, biophysics, and therapeutics.

Effect of dicationic gemini surfactants 16–s‐16 (s = 4, 5, 6) on the ninhydrin‐dipeptide (glycyl‐tyrosine) reaction

AbstractThe effect of dicationic gemini surfactants H33C16(CH3)2N+‐(CH2)s‐N+(CH3)2 C16H33, 2Br− (s= 4, 5, 6) on the reaction of a dipeptide glycyl–tyrosine (Gly–Tyr) with ninhydrin has been studied spectrophotometrically at 70°C and pH 5.0. The reaction follows first‐ and fractional‐order kinetics, respectively, in [Gly–Tyr] and [ninhydrin]. The gemini surfactant micellar media are comparatively more effective than their single chain–single head counterpart cetyltrimethylammonium bromide (CTAB) micelles. Whereas typical rate constant (kΨ) increase and leveling‐off regions, just like CTAB, are observed with geminis, the latter produces a third region of increasing kΨ at higher concentrations. This subsequent increase is ascribed to the change in the micellar morphology of the geminis. The pseudophase model of micelles was used to quantitatively analyze the kΨ − [gemini] data, wherein the micellar‐binding constants KS for [Gly–Tyr] and KN for ninhydrin were evaluated. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 800–809, 2012

Oxidative degradation of dipeptide (glycyl–glycine) by water-soluble colloidal manganese dioxide in the aqueous and micellar media

The kinetics of the oxidative degradation of dipeptide glycyl–glycine (Gly-Gly) by water-soluble colloidal MnO 2 in acidic medium has been studied by employing visible spectrophotometer in the aqueous and micellar media at 35 °C. To obtain the rate constants as functions of [Gly-Gly], [MnO 2] and [HClO 4], pseudo-first-order conditions were maintained in each kinetic run. The first-order-rate is observed with respect to [MnO 2], whereas fractional-order-rates are determined in both [Gly-Gly] and [HClO 4]. The addition of sodium pyrophosphate and sodium fluoride has composite effects (catalytic and inhibition). The reaction proceeds through the fast adsorption of Gly-Gly on the surface of the colloidal MnO 2. The observed results are discussed in terms of Michaelis–Menten/Langmuir–Hinshelwood model. The Arrhenius and Eyring equations are found valid for the reaction over a range of temperatures and different activation parameters have been evaluated. A probable reaction mechanism, in agreement with the observed kinetic results, has been proposed and discussed. The influence of changes in the surfactant concentrations on the observed rate constant is also investigated and the reaction followed the same type of kinetic behavior in micellar media. The pseudo-first-order rate constant ( k ψ) is found to increase about two-fold with increase in [TX-100]. The catalytic effect of nonionic surfactant TX-100 is explained in terms of the mathematical model proposed by Tuncay et al.

Copper(II) complexes with hydroxyl-containing dipeptides glycyl- L -serine and L -seryl- L -tyrosine

Dipeptides glycyl- L -serine and L -seryl– L -tyrosine are tridentate ligands in coordination with Cu(II) through their NH2−, N–(from deprotonated amide group) and O–atom (by COO- group), forming [CuII(LH−1)H2O]. The forth position of square-planar geometry of Cu2+ is occupied by H2O as terminal ligand. Solid-state linear dichroic IR-spectroscopy, UV-Vis, mass spectrometry with ESI and FAB, tandem mass spectrometry (HPLC-MS/MS), TGV and DSC methods, EPR and magnetochemistry data prove the formation of five-membered chelate rings with participation of Cu2+ both in solution and in solid state.

New peroxovanadium compounds containing biogenic co-ligands: synthesis, stability and effect on alkaline phosphatase activity

A set of new diperoxovanadate(V) complexes with the dipeptides glycyl–glycine or glycyl–leucine as ancillary ligands of the type, A[VO(O2)2(peptide)(H2O)] · H2O, A = Na or K have been synthesized and characterized by elemental analysis, thermal analysis, magnetic susceptibility and spectral studies. The complexes contain side-on bound peroxo groups and a dipeptide zwitterion as co-ligand, binding the metal center unidentately through O (carboxylate) atom. The compounds are highly stable toward decomposition in solutions of acidic as well as physiological pH and serve as weak substrates to catalase, undergoing degradation in the presence of the enzyme at a rate much slower than H2O2. The compounds stoichiometrically oxidize GSH to GSSG. On comparing the GSH oxidizing ability of these compounds with those of previously reported peroxotungsten compounds containing similar co-ligands, a significant difference was noted. The compounds induce a strong inhibitory effect on alkaline phosphatase activity with a potency higher than that of the free peptides, vanadate, or peroxovanadate.

Kinetics and mechanism of interaction of dipeptide (glycyl–glycine) with ninhydrin in aqueous micellar media

AbstractThe rates of reaction between ninhydrin and dipeptide glycyl–glycine (Gly–Gly) have been determined by studying the reaction spectrophotometrically at 70°C and pH 5.0 in aqueous and in aqueous cationic micelles of cetyltrimethylammonium bromide (CTAB). The reaction follows first‐ and fractional‐order kinetics, respectively, in [Gly–Gly] and [ninhydrin]. The observed rate constant is affected by [CTAB] changes and the maximum rate enhancement is ca. three‐fold. As the kψ − [CTAB] profile shape is characteristic of bimolecular reactions catalyzed by micelles, the catalysis is explained in terms of the pseudo‐phase model of the micelles (proposed by Menger and Portnoy and developed by Bunton and Romsted). The presence of inorganic salts (NaCl, NaBr, Na2SO4) does not reveal any regular effect but the data with organic salts (NaBenz, NaSal) show an increase in the rate followed by a decrease. The kinetic data have been used to calculate the micellar binding constants KS for Gly–Gly and KN for ninhydrin and the respective values are 317 and 69 mol−1 dm3. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 643–650, 2006

Determination of prolidase activity using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Proline-containing peptides of the X-proline type are cleaved by the dipeptidase prolidase. The classical method of prolidase assay relied on the colorimetric estimation of the liberated proline with ninhydrin using acidic media and heat. This method, however, gave inconsistent results due to the nonspecificity of the ninhydrin color reaction. We report here a method for the detection of the liberated proline using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Human sera were incubated with a mixture containing the dipeptide glycyl–proline in Tris–HCl supplemented with manganese at 37 °C for 24 h. The samples were precipitated with trifluoroacetic acid and centrifuged. An aliquot of the supernatant was mixed with an equal volume of ferulic acid solution. An aliquot from this mixture was spotted on a stainless steel mass spectrometry grid and analyzed using MALDI-TOF mass spectrometry. The activity of the enzyme was determined by the complete disappearance of the glycyl–proline peak with the concomitant appearance of the proline peak and can be expressed in terms of the ratio of the area beneath the proline to the area beneath the glycyl–proline peak. Subjects homozygous for prolidase deficiency had a ratio ranging from 0.006 to 0.04 while obligatory heterozygotes had a ratio ranging from around 1.1 to 2.4. Normal subjects had ratios ranging from 9 to 239. Using this method we have unambiguously identified subjects with homozygous or heterozygous prolidase deficiency. In addition to the advantage of rapid sample preparation time, this method is highly specific, reproducible, and sensitive.

Racemic dipeptide glycyl-DL-leucine at 120 K.

The structure of glycyl-DL-leucine, C(8)H(16)N(2)O(3), has been determined at 120 K by single-crystal X-ray diffraction. In addition to three N-H.O-type hydrogen bonds of the positively charged RNH(3)(+) group of the zwitterionic molecule, an intermolecular N-H. O contact exists between the peptide bond and the carboxylate group. Four hydrogen-bond cycles were identified, giving a complex pattern.

Acoustic absorption due to proton transfer in solutions of proteins, peptides and amino acids at neutral pH.

Measurements of ultrasonic absorption in the frequency range 2 to 60 MHz have been made on solutions of the amino acid histidine, dipeptides glycyl tyrosine and histidyl tyrosine, and proteins lysozyme and bovine serum albumin. Measurements were carried out at 37 degrees C and covered the pH range 6.8 to 7.7. Mechanisms for the observed excess acoustic absorption involving bimolecular and intramolecular proton transfer are considered.

Thermodynamic properties of peptide solutions. Part 12. Enthalpies of dilution of aqueous solutions of some glycyl dipeptides at 298.15 K

Enthalpies of dilution at 298.15 K of aqueous solutions of the dipeptides glycyl- l-valine, glycyl- d-leucine, glycyl- l-asparagine, glycyl- l-threonine, glycyl- dl-threonine and glycyl- dl-serine have been determined using flow microcalorimetry. The results obtained were used to determine the enthalpic interaction coefficients that characterise pair interactions of the peptides in aqueous solution. These coefficients were compared with those for other dipeptides and also with those for some amino acids.

Identification of identical binding polypeptides for cephalosporins and dipeptides in intestinal brush-border membrane vesicles by photoaffinity labeling

The uptake of a photolabile derivative of the orally effective cephalosporin cephalexin, N-(4-azidobenzoyl)cephalexin, was investigated in brush-border membrane vesicles. The compound was taken up into the intravesicular space and inhibited the active uptake of cephalexin in a concentration-dependent manner. Therefore, this probe interacts with the transport system shared by α-aminocephalosporins and dipeptides. Photoaffinity labeling of brush-border membrane vesicles from rat small intestine with N-(4-azido [3,5,- 3H]benzoyl) derivatives of the cephalosporin cephalexin and the dipeptide glycyl- l-proline resulted in the covalent incorporation of radiaoctivity into membrane polypeptides with apparent molecular weights of 127000, 100000, 94000 and 86000, the polypeptide of molecular weight 127000 being predominantly labeled. The specificity of labeling was demonstrated by a decrease in the labeling of the polypeptide of apparent molecular weight 127000 in the presence of β-lactam antibiotics and dipeptides, whereas glucose, taurocholate or amino acids had not effect on the labeling pattern. These data demonstrate an interaction of cephalosporins and dipeptides with a common membrane protein of molecular weight 127000, which could be a component of the intestinal transport system(s) responsible for the uptake of orally effective cephalosporins and dipeptides.

Structure-activity relationships for the lipid-mobilising action of locust adipokinetic hormone. Synthesis and activity of a series of hormone analogues.

A series of compounds structurally related to adipokinetic hormone, the decapeptide neurohormone less than Glu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-Thr-NH2, have been prepared by synthesis and by enzymic cleavages of synthetic hormone. Their relative agonist activities in mobilising lipids over a fixed time interval (1 h) in locusts were assessed. The similar time courses for lipid release shown by two of the peptide analogues and adipokinetic hormone suggest that the analogues and the hormone are transported to the receptors on the fat body cells, and are also degraded, at similar rates. Consequently, the analogue activities can be correlated with the structural requirements of the locust fat body hormone receptors. The requirements for activity demonstrated in this study are as follows. Residues 1--8 from the N-terminus are necessary to elicit some activity (20%). Residues 5 and 7 in the octapeptide can be changed without affecting activity but L-pyroglutamic acid as the N-terminal residue is necessary formaximum activity both in the octapeptide and the decapeptide. Full activity is achieved only by adding the dipeptide glycyl threonine amide to the active octapeptide 'core'. In the decapeptide, residues cannot be interchanged to the same extent as in the octapeptide without reducing activity. The peptide probably has to be uncharged. Inactive analogues of seven residues or less do not interfere in the hormone-receptor interaction.

Proteolytic enzymes of Penicillium janthinellum

Abstract 1. 1. The properties of an extracellular peptidase (peptidase B) of Penicillium janthinellum which was separated by paper electrophoresis from a preparation of peptidase A, have been studied. 2. 2. Unlike peptidase A, peptidase B will not activate trypsinogen. 3. 3. Peptidase B is active on a number of peptides, none of which are substrates for peptidase A. Peptidase B is especially active on Cbz- l -glutamyl- l -phenylalanine, Cbz- l -glutamyl- l -tyrosine and Cbz- l -tyrosyl- l -glutamic acid, and while inactive on Cbz-glycyl- l -phenylalanine, it promotes hydrolysis of the free dipeptide glycyl- l -phenylalanine. 4. 4. The hydrolysis of Cbz- l -glutamyl- l -tyrosine by peptidase B takes place optimally at pH 4.7. The extent of inhibition imposed by a range of anions on this hydrolysis has been recorded, and the effect of selected inhibitors on the kinetics of the reaction studied. The inhibition imposed by salts of the fatty acid series is proportional to the molecular weight of the inhibitor. 5. 5. None of a series of metal salts tested increased the activity of the enzyme, and ferric, cadmium and barium ions were inhibitory. 6. 6. The enzyme is not inhibited by sulfhydryl reagents. 7. 7. A value for Km of 5·10−4 M of Cbz- l -glutamyl- l -tyrosine was obtained.

Linear Titration Curves of Acids and Bases

The Henderson-Hasselbalch equation, by a simple transformation, becomes pH - pK = pA - pB, where pA and pB are the negative logarithms of acid and base concentrations. Sigmoid titration curves then reduce to straight lines; titration curves of polyelectrolytes, to families of straight lines. The method is applied to the titration of the dipeptide glycyl aminotricarballylic acid, with four titrable groups. Results are expressed as Cartesian and d'Ocagne nomograms. The latter is of a general form applicable to polyelectrolytes of any degree of complexity.