Peptides concentrations

The reversibility of the reaction guarantees that each measurement represents an equilibrium state. Furthermore, the position of the equilibrium turned out to be independent of the initial peptide concentration. Therefore, the thermodynamic parameters... 

M30. Mitaka, C., Nagura, T., Sakanishi, N Tsunoda, Y., and Toyooka, H., Plasma a-atrial natriuretic peptide concentrations in acute respiratory failure associated with sepsis Preliminary study. Crit. Care Med. 18, 1201-1203 (1990). 

A (3 fibril formation an identifiable nucleating species has yet be isolated. Direct observation has been made difficult by the small size of the (3 peptide, which has an effective hydrodynamic radius of 4 nm [98-100], and by the apparent low abundance of nucleating species due to the low probability of their formation. Such species would be formally akin to an enzyme transition state that is usually kinetically inferred or sometimes trapped with certain kinds of inhibitor. In disaggregated, ultrafiltered (20 nm pore size) preparations, less than 1% of the molar peptide concentration is inferred to be present as seeds or nuclei determined by the kinetics of fibril formation [101]. 

The processes of both seed formation and fibril extension are dependent on temperature and on peptide concentration, with 37°C being required for establishing equilibrium within 24 h with 30 pM Pi 4o- A full description of the assay system may be found elsewhere [97,117], A 4 h reaction time is typically within the linear portion of the time course. This nucleus-dependent assay detects mainly inhibitors that are substoichiometric with the monomeric peptide, which is present at high concentration. It is relatively insensitive to inhibitors that target the monomeric peptide. Whether the inhibitors interact with the growing end of a seed or with a low abundance conformational form of the p peptide that is competent to add to the seed is difficult to determine at this time. Similar dose-response curves are obtained for Congo Red as an inhibitor with either thioflavin T (ThT) fluorescence or filtration of radioiodinated peptide readouts (Fig. 4) Caveats in the interpretation of both the ThT and radiometric filtration assays for the evaluation of putative inhibitors are discussed elsewhere [97]. 

A superspiral consisting of two spirals (coiled coil), known as the leucine zip, is formed in this sequence via dimerisation. The condensation reaction, carried out in the aqueous phase, involves two peptide fragments which contain 15 and 17 amino acid residues respectively. Activation takes place via thioester formation (see Sect. 5.3.1). The ligation to a complete GCN4 matrix gives a new 32 amino acid peptide, which can itself serve as a matrix. The autocatalytic reaction exhibits a parabolic increase in the peptide concentration (caused by product inhibition see Section 6.4). 

Figure 7.11 Immunostain result that demonstrates a lower level of sensitivity, in that only the highest peptide concentration is stained. The HER2+ tumor tissue (left slide) is also relatively unstained. See color insert.

Peptide concentration Peptide concentration. Peptide oonaenlralion Peptide concentration... 

For the orientation-based structure analysis of MAPs, uniformly oriented lipid bilayers are typically prepared on solid supports as illustrated in Fig. 2 [23, 47, 55]. These mechanically oriented membranes are advantageous for static ssNMR experiments, as they provide a robust way to orient a sample with any desired lipid composition, peptide concentration, and at any desired temperature. The lipids... 

Fig. 10. (A) Far-ultraviolet CD spectra of fragment 206-316 of thermolysin at different temperatures in 20 raM Tris-HCl buffer, pH 7.2. Numbers near the curves indicate temperature in degrees Celsius. The peptide concentration was 0.2 mg/ml. (B) Temperature dependence of [0]/[0]o at 220 nm of fragment 206-316, where [0]o is the mean residue ellipiticity at 22°C. Reprinted with permission from Peptides Proceedings of the Fifth American Peptide Symposium, John Wiley Sons, Inc., 1977. Copyright by John Wiley Sons, Inc.

Over 300 peptides isolated in our laboratory were studied in one or more tumor or normal cell cultures [39-44]. Part of the results obtained is summarized in Table 2.3. Over 75% of the peptides showed pronounced proliferative or antiproliferative activity in at least one cell type (Fig. 2.3). As a rule, tumor cells are more sensitive to peptide action. Besides the cell type, experimental conditions such as cell density or composition of the culture medium also affected the overall effect. In several cases (13%, Fig. 2.3) even the sign of the effect was peptide concentration dependent. Generally, experiments with cell cultures conform with the view that the main physiological function of cell and tissue peptidomes is control of long term processes and the homeostatic balance (i.e. cell differentiation, proliferation and elimination). The overall effect of peptide pools is achieved by concerted action of total sets of peptides rather than by single components. The molecular mechanisms of peptide action in cells requires concrete study in each individual case and are the subject of current research. 

Morley JE, Yamada T, Walsh JH, Lamers CB, Wong H, Shulkes A, Damassa DA, Gordon J, Carlson HE, Hershman JM. (1980). Morphine addiction and withdrawal alters brain peptide concentrations. Life Sci. 26(26) 2239-44. 

Fig. 2 Solid state F-NMR spectra of GS-3/3 in oriented DMPC bilayers, measured at 25 °C according to published procedures [17-19,22]. Samples are prepared with a peptidedipid molar ratio of 1 80 (A), 1 40 (B), and 1 20 (C). The arrows indicate the signals emerging at high peptide concentration, corresponding to a new re-aligned state of the peptide. The dashed line shows respective powder pattern of the lyophUized peptide...

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