title: Examination of polypeptide beta-sheet structure in solutions and thin layers: determination of the concentration and the 'critical aggregation concentration' using a cyanine dye as sensor.
abstract: In the visible spectra of some cyanine dyes a bathochromic shift of the dye monomer band was observed on the preconditions that: (1) beta-sheet containing polypeptides (denotes also proteins) were presented; and (2) these polypeptides were embedded in a layer or aggregated in solution. The band with the polypeptides which contained only the alpha-helix did not shift. In several cases the absorbance lifetime of the shifted band was limited. This was caused by dye self-association at the polypeptide surface, but there were enough quantities for this lifetime to obtain exact analytical measurements. These were executed quantitatively (100-20% beta-sheet), qualitatively (to about 10% beta-sheet) and moreover for the determination of the 'critical aggregation concentration' (cac). The applications of the dye sensor in biophysics, medicine and pharmacy were discussed.
authors.affiliation: Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Berlin, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Hermel
authors.forename: U
authors.initials: U
authors.lastname: De Rossi
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D002232:Carbocyanines / Q000737:chemistry*; D002942:Circular Dichroism; D005456:Fluorescent Dyes / Q000737:chemistry*; D008027:Light; D008567:Membranes, Artificial; D015335:Molecular Probes; D010455:Peptides / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry; D017433:Protein Structure, Secondary; D012542:Scattering, Radiation; D012996:Solutions; D013053:Spectrophotometry
chemical_list: D001704:Biopolymers; D002232:Carbocyanines; D005456:Fluorescent Dyes; D008567:Membranes, Artificial; D015335:Molecular Probes; D010455:Peptides; D012996:Solutions; D011107:Polylysine