Folding and aggregation in mixed dimers of gramicidin D

2005 ◽  
pp. 389-391
Author(s):  
William L. Duax ◽  
Brian M. Burkhart ◽  
David A. Langs ◽  
Walter A. Pangborn
Keyword(s):  
Gramicidin D

scholarly journals A Rapid Fluorescence-Based Microplate Assay to Investigate the Interaction of Membrane Active Antimicrobial Peptides with Whole Gram-Positive Bacteria

Antibiotics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 92 ◽  
Author(s):  
Gerard Boix-Lemonche ◽  
Maria Lekka ◽  
Barbara Skerlavaj
Keyword(s):  
Antimicrobial Peptides ◽  
Staphylococcus Epidermidis ◽  
Membrane Depolarization ◽  
Membrane Permeabilization ◽  
Microplate Assay ◽  
Membrane Systems ◽  
Gram Positive Bacteria ◽  
Gramicidin D ◽  
Membrane Effects ◽  
Specific Membrane

Background: Membrane-active antimicrobial peptides (AMPs) are interesting candidates for the development of novel antimicrobials. Although their effects were extensively investigated in model membrane systems, interactions of AMPs with living microbial membranes are less known due to their complexity. The aim of the present study was to develop a rapid fluorescence-based microplate assay to analyze the membrane effects of AMPs in whole Staphylococcus aureus and Staphylococcus epidermidis. Methods: Bacteria were exposed to bactericidal and sub-inhibitory concentrations of two membrane-active AMPs in the presence of the potential-sensitive dye 3,3′-dipropylthiadicarbocyanine iodide (diSC3(5)) and the DNA staining dye propidium iodide (PI), to simultaneously monitor and possibly distinguish membrane depolarization and membrane permeabilization. Results: The ion channel-forming gramicidin D induced a rapid increase of diSC3(5), but not PI fluorescence, with slower kinetics at descending peptide concentrations, confirming killing due to membrane depolarization. The pore-forming melittin, at sub-MIC and bactericidal concentrations, caused, respectively, an increase of PI fluorescence in one or both dyes simultaneously, suggesting membrane permeabilization as a key event. Conclusions: This assay allowed the distinction between specific membrane effects, and it could be applied in the mode of action studies as well as in the screening of novel membrane-active AMPs.

Role of chloride in constriction of descending vasa recta by angiotensin II

2001 ◽  
Vol 280 (6) ◽  
pp. R1878-R1886 ◽  
Author(s):  
Zhong Zhang ◽  
James M. C. Huang ◽  
Malcolm R. Turner ◽  
Kristie L. Rhinehart ◽  
Thomas L. Pallone
Keyword(s):  
Membrane Potential ◽  
Chloride Channels ◽  
Channel Blocker ◽  
Chloride Ion ◽  
Ang Ii ◽  
Vasa Recta ◽  
Gramicidin D ◽  
Chloride Channel Blocker ◽  
Increased Activity

We investigated the dependence of ANG II (10−8 M)-induced constriction of outer medullary descending vasa recta (OMDVR) on membrane potential (Ψm) and chloride ion. ANG II depolarized OMDVR, as measured by fully loading them with the voltage-sensitive dye bis[1,3-dibutylbarbituric acid-(5)] trimethineoxonol [DiBAC4(3)] or selectively loading their pericytes. ANG II was also observed to depolarize pericytes from a resting value of −55.6 ± 2.6 to −26.2 ± 5.4 mV when measured with gramicidin D-perforated patches. When measured with DiBAC4(3) in unstimulated vessels, neither changing extracellular Cl− concentration ([Cl−]) nor exposure to the chloride channel blocker indanyloxyacetic acid 94 (IAA-94; 30 μM) affected Ψm. In contrast, IAA-94 repolarized OMDVR pretreated with ANG II. Neither IAA-94 (30 μM) nor niflumic acid (30 μM, 1 mM) affected the vasoactivity of unstimulated OMDVR, whereas both dilated ANG II-preconstricted vessels. Reduction of extracellular [Cl−] from 150 to 30 meq/l enhanced ANG II-induced constriction. Finally, we identified a Cl−channel in OMDVR pericytes that is activated by ANG II or by excision into extracellular buffer. We conclude that constriction of OMDVR by ANG II involves pericyte depolarization due, in part, to increased activity of chloride channels.

Effect of methyl viologen on slow secondary fluorescence kinetics associated with photosynthetic carbon assimilation in intact isolated chloroplasts

1985 ◽  
Vol 226 (1243) ◽  
pp. 237-247 ◽  
Keyword(s):  
Methyl Viologen ◽  
Carbon Assimilation ◽  
Pentose Phosphate ◽  
Induction Phase ◽  
Atp Production ◽  
Gramicidin D ◽  
Photosynthetic Carbon ◽  
Photosynthetic Carbon Assimilation ◽  
Isolated Chloroplasts ◽  
Secondary Fluorescence

Methyl viologen in catalytic amounts induces pronounced secondary kinetics in fluorescence in intact isolated chloroplasts performing photosynthetic carbon assimilation. These transient increases in fluorescence and oscillations were associated with the induction phase of O 2 evolution in a similar manner to the transient ‘shoulder’ detected previously (Z. G. Cerović, M. N. Sivak and D. A. Walker, Proc . R . Soc . Lond . B 220, 327–338 (1984)). Experiments with the addition of antimycin A and gramicidin D demonstrated that methyl viologen induced an increased ATP production linked to pseudocyclic electron transport. The adjustment of ATP and NADPH production to meet the requirements of the reductive pentose phosphate pathway during induction is thought to be the cause of the detected transients and oscillations in fluorescence.

Anomalous uncoupling of photophosphorylation by palmitic acid and by gramicidin D

Biochemistry ◽  
1987 ◽  
Vol 26 (25) ◽  
pp. 8295-8302 ◽  
Author(s):  
Uri Pick ◽  
Meira Weiss ◽  
Hagai Rottenberg
Keyword(s):  
Palmitic Acid ◽  
Gramicidin D
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