Stephanie M. Cope

Studies of inactivation of encephalomyocarditis virus, M13 bacteriophage, and Salmonella typhimurium by using a visible femtosecond laser: insight into the possible inactivation mechanisms

We report experimental results on the inactivation of encephalomyocarditis virus, M13 bacteriophage, and Salmonella typhimurium by a visible femtosecond laser. Our results suggest that inactivation of virus and bacterium by a visible femtosecond laser involves completely different mechanisms. Inactivation of viruses by a visible femtosecond laser involves the breaking of hydrogen∕hydrophobic bonds or the separation of the weak protein links in the protein shell of a viral particle. In contrast, inactivation of bacteria is related to the damage of their DNAs due to irradiation of a visible femtosecond laser. Possible mechanisms for the inactivation of viruses and bacteria are discussed.

Slow Internal Dynamics and Charge Expansion in the Disordered Protein CGRP: A Comparison with Amylin

We provide the first direct experimental comparison, to our knowledge, between the internal dynamics of calcitonin-gene-related peptide (CGRP) and amylin (islet amyloid polypeptide, IAPP), two intrinsically disordered proteins of the calcitonin peptide family. Our end-to-end contact formation measurements reveal that in aqueous solution (i.e., in the absence of structure-inducing organic solvents) CGRP preferentially populates conformations with short end-to-end distances. However, the end-to-end distance of CGRP is larger than that of IAPP. We find that electrostatic interactions can account for such a difference. At variance with previous reports on the secondary structure of CGRP, we find that the end-to-end distance of the peptide increases with decreasing pH and salt concentration, due to Coulomb repulsion by charged residues. Interestingly, our data show that the reconfiguration dynamics of CGRP is significantly slower than that of human IAPP in water but not in denaturant, providing experimental evidence for roughness in the energy landscape, or internal friction, in these peptides. The data reported here provide both structural and dynamical information that can be used to validate results from molecular simulations of calcitonin family peptides in aqueous solution.

Cyclic N-Terminal Loop of Amylin Forms Non Amyloid Fibers

We report for the first time, to our knowledge, that the N-terminal loop (N_loop) of amylin (islet amyloid polypeptide (IAPP) residues 1-8) forms extremely long and stable non-β-sheet fibers in solution under the same conditions in which human amylin (hIAPP) forms amyloid fibers. This observation applies to the cyclic, oxidized form of the N_loop but not to the linear, reduced form, which does not form fibers. Our findings indicate a potential role of direct N_loop-N_loop interactions in hIAPP aggregation, which has not been previously explored, with important implications for the mechanism of hIAPP amyloid fiber formation, the inhibitory action of IAPP variants, and the competition between ordered and disordered aggregation in peptides of the calcitonin peptide family.

Photonic approach to the selective inactivation of viruses with a near-infrared ultrashort pulsed laser

We report a photonic approach for selective inactivation of viruses with a near-infrared ultrashort pulsed (USP) laser. We demonstrate that this method can selectively inactivate viral particles ranging from nonpathogenic viruses such as M13 bacteriophage, tobacco mosaic virus (TMV) to pathogenic viruses like human papillomavirus (HPV) and human immunodeficiency virus (HIV). At the same time sensitive materials like human Jurkat T cells, human red blood cells, and mouse dendritic cells remain unharmed. Our photonic approach could be used for the disinfection of viral pathogens in blood products and for the treatment of blood-borne viral diseases in the clinic.