OPTICAL-PROPERTIES OF HORSERADISH-PEROXIDASE FROM 0.13 TO 2.5-MU-M

Measurements of optical characteristics such as light scattering and f luorescence of components in bacterial cells have been used to sort ce lls and to identify different classes of bacteria in a mixed suspensio n. More detailed studies require a knowledge of the optical properties of individual components of the cells. Because cells are composed lar gely of proteins, a measurement of the optical constants of horseradis h peroxidase, a globular protein, would permit modeling of the refract ive index profiles of complex inhomogeneous structures such as a bacte rial spore. Spectral reflectance and transmittance measurements combin ed with Kramers-Kronig analyses have been used to obtain the real (n) and imaginary (k) parts of the complex refractive index N = n + ik of horseradish peroxidase over the wavelength interval from 0.13 to 2.5 m u m. Samples were in the form of thin solid films, pressed pellets, an d solutions in water. For wavelengths less than 0.6 mu m, good agreeme nt was obtained between the optical constants of the material derived from measurements made on the solid films and on the solutions in wate r. (C) 1997 John Wiley & Sons, Inc.