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Ajay Pande, Kalyan S. Ghosh, Jayanti Pande; Structural Plasticity And Membrane Interaction Of An Authentic Human Lens alphaA67-75 Peptide. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2281.
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The αA67-75 peptide has been shown to be present in the nucleus and cortex of the human lens, in the water-soluble as well as insoluble fractions. This in vitro study was undertaken to determine whether this nona-peptide could potentially affect lens organization and function.
αA67-75 was synthesized by Genscript and was about 96% pure. Peptide aggregation was monitored by static light scattering using the Zetasizer (Malvern) and DPH (1, 6-diphenyl-1, 3, 5-hexatriene) fluorescence emission at 425nm. The peptide was incorporated into liposomes made with synthetic lipids modeling lens-specific membranes. Leakiness of such liposomes, due to peptide incorporation, was measured by entrapping carboxyfluorescein dye in the liposomes. Secondary structure of the peptide in aqueous solution and liposomes was determined by far-UV circular dichroism (CD). Formation of amyloid structure was investigated by several methods: Infra-red spectroscopy, thioflavin T fluorescence emission, and by the induced CD using the congo-red dye.
The αA67-75 amphiphilic nona-peptide, 67DRDKFVIFL75, forms a beta-strand in aqueous solution, and gives rise to a micellar aggregate with a critical micellar concentration of ~ 0.3μM. The peptide, when incorporated into liposomes made of synthetic lipids modeling lens membranes, renders them leaky. However, unlike the effect of many other known peptides, these liposomes remain stable and do not show any abnormal aggregation property. We also confirmed that the peptide spontaneously forms amyloids, as has been reported earlier by other investigators.
The αA67-75 peptide appears to form micellar aggregates even below microMolar concentrations. It is membrane active and capable of disrupting the membrane bilayer structure. In addition to its tendency to form amyloids, this peptide shows several characteristics all potentially contributing to increased light scattering in the lens in vivo.
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