Membrane mimicking

It is obvious why the spectroscopist wants to investigate the structure of integral membrane proteins or enzymes, whose biological action is linked to the presence of phospholipids such as phospholipase, in a membrane-mimicking environment Why such an environment should also be used for other peptides like hormones becomes more clear when we take into account the membrane compartment theory [10-12] as postulated by R. Schwyzer. This theory states that peptides that target membrane-embedded receptors... 

The central part of cell walls is a membrane consisting of complex self-assembled structures with built-in channels that execute complicated functions, e.g., the transport of ions briefly discussed in Section 5.3.4). Creating artificial membranes mimicking the functioning of biological membranes is one of the important tasks of supramolecular chemistry. 

Fig. 27 Lamellar-cubic transition in membrane-mimicking lipid composition induced by mixing with C18 1C10-EPC, recorded by X-ray diffraction at heating scan rate of l°C/min. (reproduced from [112] copyright (2007) National Academy of Sciences, USA)...

The tertiary structure of retrocyclin-2 in a membrane-mimicking environment was determined recently and consists of a well-defined (3-hairpin braced by the three laddered disulphide bonds.193 Analytical ultracentrifugation and NMR diffusion experiments indicated that retrocyclin-2 self-associates to form a trimer. Self-association is an important feature of some antimicrobial peptides but the role of this self-association in the mechanism of action of the retrocyclins is yet to be determined. 

Chaloin, L., Vidal, P., Heitz, A., et al. (1997) Conformations of primary amphi-pathic carrier peptides in membrane mimicking environments. Biochemistry 36, 11,179-11,187. 

Several classes of lipids common for the biomembranes can form inverted nonlamellar phases under physiologic conditions (4). The principle ones are phosphatidylethanolamines and monogalactosyldiglycerides. Also, cardiolipins and phos-phatidic acids can form inverted phases in the presence of divalent cations, and phosphatidylserines and phosphatidic acids both form inverted phases at low pH. Moreover, biomembrane lipid extracts and membrane-mimicking lipid compositions form nonlamellar phases if heated above physiologic temperatures, dehydrated, or treated with divalent cations (5-7). 

Schlegel, B., Sippl, W., Holtje, H.-D. Molecular dynamics simulations of bovine rhodopsin influence of protonation states and different membrane-mimicking environments. J. Mol. Model. 2005,12, 49-64. 

Lin BT-Y, Colby T, Gown AM, et al. Malignant vascular tumors of the serous membranes mimicking mesothelioma A report of 14 cases. Am J Surg Pathol. 1996 20 1431-1439. 

Recent studies of Ananthanarayanan (122) have shown that various peptide hormones are capable of inducing Ca2+ influxes into phosphatidylcholine vesicles. The observed affinity of gastrin and CCK as well as of their lipo-derivatives for Ca2+ in membrane mimicking environments led us to examine rates of Ca2+ influxes induced by these hormones. 

The NMR structure of ASYN bound to SDS micelles, commonly used for membrane mimicking, revealed a break in the helix, resulting in two antiparallel alpha-helices [132]. This model was confirmed by distance measurements exploiting SDSL EPR utilizing 13 different ASYN double mutants each containing 2 spin-labeled cysteines (horseshoe model. Fig. 12) [137]. 

Fig.l Membrane-mimicking environments, (a) Bacteriorhodopsin spin labeled at position 36 and 46 with the software MMM. (b) Schematic drawings of bacteriorhodopsin inserted in micelle, liposome, membrane bilayer and nanodisc. The liposome is not drawn to scale... 

Overdose of saffron has been associated with vomiting, bleeding, vertigo, confusion, and yellowing of the skin and mucous membranes (mimicking jaundice) (Frank 1961 Wichtl 2004). 

Overdose of saffron (maximum daily dose listed as 1.5 g) has been associated with vomiting, uterine bleeding, bloody diarrhea and urine, bleeding from the nose, lips, and eyelids, convulsions, intestinal colic, vertigo, confusion, and yellowing of the skin and mucous membranes (mimicking jaundice) (Bensky et al. 2004 Wichtl 2004). 

Thus the low molecular weight PHB-polymer (19-20 monomer units) can be used effectively for preparation of artificial ion channels in cell membranes mimicking natural ones. The model of channels proposed contains two helices the outer one containing poly-(R)-3 hydroxybutanoate, complexed by hydrogen bonding with the inner helix of poly(-Ca phosphonate) (Fig 1). 

Fig. 3 Lung-on-a-chip platfom (Adapted from [15]). (A) PDMS-based membrane mimicking the alveolar-capillary barrier and vacuum based deformation controller mimicking the breathing movements of the lung. (B) Schematic representations of lung size change during the inhalation process. (C) The bonding and alignment of three layer PDMS structures to form the devices.

NMR spectroscopy in a membrane-mimicking environment has been used to study the interactions of interleukin-8 with the human chemokine receptor CXCRl and how the phosphorylation of encephalins changes their structures while increasing their solubility and ability to cross the blood-brain barrier. " ... 

Butruk-Raszeja B, Trzaskowski M, Ciach T. Cell membrane-mimicking coating for blood-contacting polyurethanes. J Biomater Appl 2014 29(6) 801-12. 

Streicher, E., Schneider, H. Polysulphone membrane mimicking human glomerular basement membrane. Lancet 322, 1136 (1983)... 

---