Contents Gramicidin

The tryptophane content of the gramicidin complex was measured by the ultraviolet absorbance47. 

The spectra exhibit several important characteristics. First, the intensity of the gauche marker bands increases with increasing temperature, particularly in the range from 34-44 °C. Second, the overall fraction of gauche conformers increases with increasing Gramicidin content. Third, there is a reversal in the relative... 

Drs. Moore and Stein of the Rockefeller Institute have studied the quantitative amino acid content of gramicidins A and B by starch chromatography. Figure 4 is an elution curve of gramicidin A. Here the concentration is estimated by the sensitive ninhydrm color test. 93% recovery of the nitrogen is accounted for. It has not proven possible... 

Whole-cell mode— perforated. This mode is similar to the conventional whole-cell mode but the cell membrane is not ruptured. Instead, small amounts of an ionophore, such as amphotericin B, nystatin, or gramicidin, are added into the electrode solution, which produce very small perforations in the membrane patch surrounded by the electrode. Only small ions (K, Na" ") and not larger ones (Ca ) or any other molecules can move freely through the formed membrane holes. This mode allows ion current recordings while the internal content of the cell is kept intact. 

Fig. 4.1 Spectra (A)-(C) show the high field expansion of proton spectra of a 50 mM solution of Gramicidin-S (3), in DMSO-d recorded at field strengths of 250, 500 and 700 MHz, respectively. The increase in dispersion, hence information content, is self-evident as field strength increases.

Photosynthetic Electron Transport. Thylakoids were isolated from spinach leaves by the method of Whitmarsh (13). Chlorophyll content was measured according to Arnon (14). The reaction medium contained 0.1 M sorbitol, 10 mM MgCl2, 10 mM NaCl, 10 mM Tricine-NaOH (pH 7.8) 0.05 mM Dichlorophenol-indophenol (DCPIP), 1 mM NH4C1, 1 pM Gramicidin D and thylakoid membranes equivalent to 5 pg chlorophyll/ml. Triplicate readings were taken 0, 15 and 30 s after illumination at 580 nM and initial rates were calculated over a range of inhibitor concentrations. ... 

Such peptide antibiotics as bacitracin, gramicidin, tyrocidine, and gramicidin S are produced by cells of various strains of Bacillus species in large quantity after exponential growth has been completed and prior to the appearance of spores. Appropriate manipulations of the amino acid and amino acid analogue content of the culture media can, in some cases, cause shifts in the proportion of the molecular species of peptides that are formed. 

Functional artificial ion channels have been reported which illustrate the general criteria. The most obvious course is to prepare oligopeptides with hi helical content (S). Other reported systems are bas on cyclo xtrin (6), polymeric crown ethers (7), and "bouquet" shaped crown ether and cyclodextrin motifs (8). One of the most active systems is a simple tris-crown ether derivative repented by Gokel for the transport of sodium ions(9). All of these systems envisage a uni- or bi-molecular transmembrane structure, similar to the gramicidin structurd paradigm. 

---