Single channels and surface potential of linear gramicidins

Gramicidin channels that have no tryptophan residues

“…The increased voltage dependence should vary as a function of the ratio of the dissociation and translocation rate constants [e.g., Andersen (1989)]-the higher the ratio, the steeper the voltage dependence. The present results [and those of Daumas et al (1989Daumas et al ( ,1991] thus suggest that the translocation rate constant is decreased as well; see also Heitz et al (1989). [This conclusion would hold unconditionally if the channels were occupied by at most one ion; but gA channels can be occupied by two Cs+ (Finkelstein & Andersen, 1981), which complicates the analysis.…”

Gramicidin channels that have no tryptophan residues

“…The increased voltage dependence should vary as a function of the ratio of the dissociation and translocation rate constants [e.g., Andersen (1989)]-the higher the ratio, the steeper the voltage dependence. The present results [and those of Daumas et al (1989Daumas et al ( ,1991] thus suggest that the translocation rate constant is decreased as well; see also Heitz et al (1989). [This conclusion would hold unconditionally if the channels were occupied by at most one ion; but gA channels can be occupied by two Cs+ (Finkelstein & Andersen, 1981), which complicates the analysis.…”

Tryptophan Contributions to the Empirical Free-Energy Profile in Gramicidin A/M Heterodimer Channels

“…For this reason, superlinear gM/Cs 1 channel-current measurements from Heitz et al (25) were given twice the weight of most other data sets in this fit to ensure that the 3B2S parameter set accurately predicted this distinctive superlinear relation. In contrast, two Heitz paradigms (25,48) showed strange secondary-rise behavior at very low voltages that could not be predicted with the 3B2S method. Because measurements made at low voltages may be less reliable, these data were given half the normal weight.…”

“…The model adequately predicted four channel current measurements from Fonseca et al (18), not shown here. Two Heitz paradigms (25,48) showed strange secondary-rise behavior at very low voltages that was difficult to predict with the 3B2S method. Because measurements made at low voltages may be less reliable, these two data sets were given a weight that was half that of most other data sets included in this fit and are not shown here.…”

“…Because measurements made at low voltages may be less reliable, these two data sets were given a weight that was half that of most other data sets included in this fit and are not shown here. (a) gA/Cs 1 /GMO measurements from Heitz et al (48). (b) gA/Cs 1 /GMO measurements from Neher et al (46).…”

Conformational transitions of gramicidin A in phospholipid model membranes. A high-performance liquid chromatography assessment

“…Finally, HPLC emerges as an exciting, powerful technique to be used in combination with other spectroscopic methods for the monitoring of other self-associating hydrophobic peptides incorporated in model membranes. In particular, due to the importance attributed to the tryptophan residues for proper functioning of gramicidin as a channel (Stark et al, 1986;Jones et al, 1986), this chromatographic approach will be of much interest for studying gramicidin analogues where tryptophan residues have been chemically modified (Prasard et al, 1983;Killian et al, 1987) or replaced by different amino acids, which have shown altered conductance behavior (Straessle et al, 1989;Heitz et al, 1989). Received May 31, 1990; Revised Manuscript Received September 28,1990 abstract:…”

Gramicidin channels that have no tryptophan residues

“…The increased voltage dependence should vary as a function of the ratio of the dissociation and translocation rate constants [e.g., Andersen (1989)]-the higher the ratio, the steeper the voltage dependence. The present results [and those of Daumas et al (1989Daumas et al ( ,1991] thus suggest that the translocation rate constant is decreased as well; see also Heitz et al (1989). [This conclusion would hold unconditionally if the channels were occupied by at most one ion; but gA channels can be occupied by two Cs+ (Finkelstein & Andersen, 1981), which complicates the analysis.…”

Tryptophan Contributions to the Empirical Free-Energy Profile in Gramicidin A/M Heterodimer Channels

“…For this reason, superlinear gM/Cs 1 channel-current measurements from Heitz et al (25) were given twice the weight of most other data sets in this fit to ensure that the 3B2S parameter set accurately predicted this distinctive superlinear relation. In contrast, two Heitz paradigms (25,48) showed strange secondary-rise behavior at very low voltages that could not be predicted with the 3B2S method. Because measurements made at low voltages may be less reliable, these data were given half the normal weight.…”

“…The model adequately predicted four channel current measurements from Fonseca et al (18), not shown here. Two Heitz paradigms (25,48) showed strange secondary-rise behavior at very low voltages that was difficult to predict with the 3B2S method. Because measurements made at low voltages may be less reliable, these two data sets were given a weight that was half that of most other data sets included in this fit and are not shown here.…”

“…Because measurements made at low voltages may be less reliable, these two data sets were given a weight that was half that of most other data sets included in this fit and are not shown here. (a) gA/Cs 1 /GMO measurements from Heitz et al (48). (b) gA/Cs 1 /GMO measurements from Neher et al (46).…”

Conformational transitions of gramicidin A in phospholipid model membranes. A high-performance liquid chromatography assessment

“…Finally, HPLC emerges as an exciting, powerful technique to be used in combination with other spectroscopic methods for the monitoring of other self-associating hydrophobic peptides incorporated in model membranes. In particular, due to the importance attributed to the tryptophan residues for proper functioning of gramicidin as a channel (Stark et al, 1986;Jones et al, 1986), this chromatographic approach will be of much interest for studying gramicidin analogues where tryptophan residues have been chemically modified (Prasard et al, 1983;Killian et al, 1987) or replaced by different amino acids, which have shown altered conductance behavior (Straessle et al, 1989;Heitz et al, 1989). Received May 31, 1990; Revised Manuscript Received September 28,1990 abstract:…”

Gramicidin channels that have no tryptophan residues

“…The increased voltage dependence should vary as a function of the ratio of the dissociation and translocation rate constants [e.g., Andersen (1989)]-the higher the ratio, the steeper the voltage dependence. The present results [and those of Daumas et al (1989Daumas et al ( ,1991] thus suggest that the translocation rate constant is decreased as well; see also Heitz et al (1989). [This conclusion would hold unconditionally if the channels were occupied by at most one ion; but gA channels can be occupied by two Cs+ (Finkelstein & Andersen, 1981), which complicates the analysis.…”

Tryptophan Contributions to the Empirical Free-Energy Profile in Gramicidin A/M Heterodimer Channels

“…For this reason, superlinear gM/Cs 1 channel-current measurements from Heitz et al (25) were given twice the weight of most other data sets in this fit to ensure that the 3B2S parameter set accurately predicted this distinctive superlinear relation. In contrast, two Heitz paradigms (25,48) showed strange secondary-rise behavior at very low voltages that could not be predicted with the 3B2S method. Because measurements made at low voltages may be less reliable, these data were given half the normal weight.…”

“…The model adequately predicted four channel current measurements from Fonseca et al (18), not shown here. Two Heitz paradigms (25,48) showed strange secondary-rise behavior at very low voltages that was difficult to predict with the 3B2S method. Because measurements made at low voltages may be less reliable, these two data sets were given a weight that was half that of most other data sets included in this fit and are not shown here.…”

“…Because measurements made at low voltages may be less reliable, these two data sets were given a weight that was half that of most other data sets included in this fit and are not shown here. (a) gA/Cs 1 /GMO measurements from Heitz et al (48). (b) gA/Cs 1 /GMO measurements from Neher et al (46).…”

Conformational transitions of gramicidin A in phospholipid model membranes. A high-performance liquid chromatography assessment

“…Finally, HPLC emerges as an exciting, powerful technique to be used in combination with other spectroscopic methods for the monitoring of other self-associating hydrophobic peptides incorporated in model membranes. In particular, due to the importance attributed to the tryptophan residues for proper functioning of gramicidin as a channel (Stark et al, 1986;Jones et al, 1986), this chromatographic approach will be of much interest for studying gramicidin analogues where tryptophan residues have been chemically modified (Prasard et al, 1983;Killian et al, 1987) or replaced by different amino acids, which have shown altered conductance behavior (Straessle et al, 1989;Heitz et al, 1989). Received May 31, 1990; Revised Manuscript Received September 28,1990 abstract:…”