Peptide contents

Dyn is not yet known, it is likely that such changes reflect variations in the activity of the associated pathways. One possible explanation is that increases in neuropeptide tissue levels are due to decreased release of the transmitter, which dunmishes the extracellular peptide metabolism and results in accumulation of these peptide substances. Another possible contributing factor is a drug-related alteration in neuropeptide synthesis. For example, Bannon et al. (1987) reported that METH administration increased the quantity of striatal messenger RNA for the SP precursor preprotachykinin. Thus, increases in peptide synthesis might contribute to increases in peptide content caused by treatment with METH or the other amphetamine analogs. 

Mucoproteins (See Section V).—Protein-carbohydrate compounds with relatively high protein or peptide content, the chemical reactions of which are predominantly protein, are known as mucoproteins. In general they do not coagulate on being heated in aqueous solution. All mucoproteins contain a hexosamine constituent. 

For this reason either of these methods is suitable only for a comparative estimation of peptide content in urine. 

The nitrogen content of this mixture amounted in the case of normal urine to 0.68-1.27% of the total nitrogen, whereas the peptides precipitated under these circumstances constituted 16.1-20.9% of all substances appearing in urine and giving the biuret reaction. The peptide mixtures obtained in identical conditions from six samples of pathological urine (liver cirrhosis and leukemia) exhibited marked differences in the nitrogen and peptide content as compared with those isolated from normal urine. 

Alkaline hydrolysis with barium, sodium, or lithium hydroxides (0.2-4 M) at 110°C for 18-70 h126-291 requires special reaction vessels and handling. Reaction mixtures are neutralized after hydrolysis and barium ions have to be removed by precipitation as their carbonate or sulfate salts prior to analysis which leads to loss of hydrolysate. Correspondingly, peptide contents are difficult to perform by this procedure. Preferred conditions for alkaline hydrolysis are 4M LiOH at 145 °C for 4-8 h where >95% of tryptophan is recovered 291 An additional inconvenience of the alkaline hydrolysis procedure is the dilution effect in the neutralization step and thus the difficult application to the analyzer if micro-scale analysis is to be performed. The main advantage is the good recovery of tryptophan and of acid-labile amino acid derivatives such as tyrosine-0-sulfate1261 (Section 6.6) as well as partial recovery of phosphoamino acids, particularly of threonine- and tyrosine-O-phosphate (Section 6.5). 

Surprisingly, the vanilloid receptor ligand capsaicin supplied the first experimental evidence for the association between SP and nociception (Gasparovic et al., 1964). Capsaicin depletes small primary afferents of at least SP, if not all of their peptide content, and this was accompanied by hypoalgesia. SP depolarizes the ventral root of an isolated rat spinal cord preparation (Konishi and Otsuka, 1974), and has also been shown to excite and/or depolarize neurons in the dorsal root (Urban et al., 1985). Furthermore, in studies on the larger laminae IV and V neurons, the selective agonist, [Sar9,... 

Extraction is an essential step when analyzing solid samples. In some cases homogenization with a solvent suffices, but in others the sample must first be coimninuted. Water, solutions of acetic acid or sodium chloride, or more complex saline solutions are used as solvents. Mixtures of water and methanol or water and ethanol are also employed. The choice of solvent depends on the degree of selectivity desired in the extraction and whether the extraction yield is intended for quantitative analysis. Optimization of the extraction procedure is required in all cases, to fit the nature of the sample to be analyzed and the range of molecular weights of the peptides to be separated. For example, water has been used as the extraction solvent for cheese (33) and legumes (34). Saline solutions have been utilized to extract peptides from meat (35-38) and flour (39,40). Benedito de Barber et al. (41) examined differences in the extractability of amino acids and short peptides in various solvents (1M acetic acid, 70% ethanol, and distilled water) they concluded that extraction with 1M acetic acid yielded the maximum amino acid and peptide contents. 

With these words Vittorio Erspamer depicted the rational basis of the pharmacological research on peptides and proteins of the amphibian skin. This 10-year period of research has shown that amphibian skin, with its generally large peptide content, offers a rich source of secretory peptide compounds, analogues of mammalian neuropeptides and hormones. 

Fujinary E, Manes JD, Bizanek R, Peptide content determination of crude synthetic peptides by reversed-phase liquid chromatography and nitrogen-specific detection with a chemiluminescent nitrogen detector, J. Chromatogr A, 743 85-89, 1996. 

Protein or peptide content should be well defined by an appropriate physio-chemical test. If the quantity of product can be well correlated to a specific biological activity (standard curve), then an elaborate physiochemical test does not need to be performed. 

The peptide concentration in the individual specimens is determined by radioimmunoassay, using a synthetic reference peptide for the standard curve. Several commercial assays are now available for hypothalamic peptides. An alternative method is the determination of peptide content in tissue extracts by an HPLC method or by mass spectrometry. 

CRH activity, by determination of the hypothalamic peptide content - the information obtained by this measurement is usually limited and and will be controlled by the feedback action of pituitary hormone release or inhibition and adrenal steroid secretion... 

The function of opioid peptides in the adrenal medulla (localized in chromaffin granules) is unknown, but such peptides may be the source of enkephalins found centrally, especially as there is evidence that pituitary opioid peptides do not fulfil this role (e.g., hypophysectomy has little effect on the enkephalin content of brain)/115) The small peptide content of bovine adrenal medulla cells after 6 days in culture has been analyzed in detail and the results are shown. 

Care must be taken when fining a sparkling wine with bentonite in order to preserve its foaming properties. Excessive use of bentonite for the fining of sparkling wine cuv es can produce a finished product that has a large bubble size and a poor bubble stability as a result of a reduction in both protein and peptide contents. Cold stabilization procedures cause both a precipitation of potassium bitartrate crystals as well as proteins because of the downward shift in pH. This precipitation of proteins... 

Table 6B.2 summarizes the data available in the literature on peptides contents of musts, wines and related substrates such as autolyzed yeasts obtained under winemaking conditions. This table also shows the fractions studied by the different authors, the type of product, the analytical methodology, the results obtained and the purpose of their research. 

To a stirred soln of l-(tert-butylsulfanyl)-l,2-hydrazinedicarbox5miorpholide (0.22g, 0.64mmol) in argon-sat. HjO (10 mL), H-Thr-Ala-Cys-Gly-Gln-Lys-Ser-Pro-OH (0.3 g, 0.32 mmol peptide content 84.9%) in argon-sat. HjO (5mL) was added dropwise at rt. After 24 h, the soln was concentrated to a small volume and the product was precipitated from EtOH/EtOAc 5neld 0.26 g (83%) peptide content 87.8% amino acid analysis Cys(StBu) 0.98 (1). 

Measurements of urine C-peptide are useful when a continuous assessment of (3-ceU function is desired or frequent blood sampling is not practical. The 24-hour urine C-peptide content (in the absence of renal failure, which produces increased levels) correlates well with fasting serum C-peptide concentration or with the sum of C-peptide concentrations in sequential specimens after a glucose load. However, the fraction of secreted C-peptide that is excreted ill the urine exhibits high intersubject and intrasubject variability, limiting the value of urine C-peptide as a measure of insulin secretion. ... 

Husley, M.G., Pless, C.M., White, B.D. Martin, R.J. (1995) IGV administration of anti-NPY antisense oligonucleotide Effects on feeding behavior, body weight, peptide content and peptide release. Regul. Pept. 59, 207-214. 

Trans cis isomerization occurs most readily at the Trp-Pro bond, so that populations of corresponding major isomers of zwitterionic forms of the peptides are comparable and constitute a 0.85-0.90 molar fraction of the total peptide content. Isomerization about Pro-Pro bonds in peptides with n > 1 results in a small population of at least two additional cis isomers. The rate constant for interchange between trans and ds isomers about the Trp-Pro bond at 298 K has been estimated to be close to 10 s (3, 35, 38), that is,... 

Na D H, DeLuca P P, Lee K C (2004). Direct determination of the peptide content in microspheres by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Analyt. Chem. 76 2669-2673. 

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