Interaction of bilayers with basic polypeptides

Abstract

Summary. The interaction of bilayers formed from glyceryl monooleate + oleic acid with basic polypeptides was studied. Copolymers of lysine with different amino acids interact with the bilayers reducing their resistance and increasing their capacitance.The largest effect was observed with the copolymer g-lysine/e-phenylalanine (1.4:1) which decreases the specific resistance by more than 3 orders of magnitude. The smallest effects on the resistance were obtained with the very hydrophilic copolymer of g-lysine/ L-serine (1.1:1). The contribution of the double-layer potential to the measured transmembrane potentials of the charged bilayers is considered and calculated for the case of the membrane containing dissociable components in the absence of interacting copolymers.The question of whether a bimolecular layer of phospholipids is a basic structure of the biological membranes was an open one for many years. Recently, calorimetric measurements [16] and X-ray diffraction data [22] have indicated that the phospholipid bilayer is indeed a structural component of at least some of the biological membranes.The model membranes have many properties similar to biological ones [20] but differ in others, especially those involving interactions with proteins.To achieve more accurate simulation of biological membranes, using phospholipid bilayers, the latter have been interacted with various other materials [20].As biological membranes contain ~20 to 80 % of protein [17] the study of interaction of bilayers with proteins is an important factor for understanding the detailed structure and function of biological membranes.The interaction of bilayers with proteins leading to changes in electrical properties was reported by several groups [1,9,15]. Recently Montal [13] described the interaction of bilayers with poly-L-lysine.Despite the above-described investigations into the properties of the protein complexes, different factors governing the lipid-protein interactions

Effect of polymyxin B on the structure and the stability of lipid layers

“…In every case polymyxin was injected underneath the lipid layer after its formation. Lipid bilayers were formed from phospholipid solutions in decane on a circular hole in a Teflon septum as described elsewhere (Bach & Miller, 1973). Phosphatidyl serine (PS) bilayers were formed and investigated at 37 ~ the other lipid bilayers at 22 ~ Different quantities of aqueous solution of polymyxin (6 mg/ml) were added on one or both sides of the formed black bilayer membranes to reach concentrations between 0.2 and 6 ~tg/ml.…”

“…It has been shown that increase in conductance and in capacitance of lipid bilayers and of monolayers can provide a measure of the extent of their penetration by polypeptides and proteins (Bach & Miller, 1973), (Miller & Rishpon, 1977), (Pagano & Miller, 1973). Phase transition in phospholipid bilayer vesicles containing the diphenyl hexatriene (DPH) fluorescence probe, affects its fluorescence polarization (Shinitzky& Barenholz, 1974).…”

Solubilities of polypeptides with hydrophobic and negatively charged side-chains into cationic artificial membrane vesicles

“…The DSAC1 was shown to be a micellar form in the low concentration range, 0.5-10 wt 0/0, of the present study. Thermograms of the DSAC1 interacting with the polypeptides showed that the polypeptides cause a little broadening of the transition peak of the DSAC1, [13] and polypeptides [5]. The decrease in AH of the transition can be explained as follows.…”

“…In addition, the binding of PLGA to the head groups of DSAC1 may also form crosslinking bridges [5] between DSAC1 vesicles, resulting in a decrease in the interaction between hydrocarbon chains perpendicular to the bilayer membrane surface. This idea was also supported by the X-ray analysis of the PLGA-DSAC1 vesicle [15], i.e., PLGA caused a relatively large increase in the bilayer thickness in the membrane vesicle, whereas the bilayer thickness was almost independent of the incorporation of PMLG.…”

“…Many works using such model systems have already been investigated by means of calorimetric [5], electrical and permeability measurements [6,7], indicating that the main interaction forces are Coulombic and hydrophobic. N 154 One of the basic approaches to this problem involves labeling of membrane systems with photoactivable groups such as fluorescent probes [8].…”