Improved Technics for the near Infrared Study of Water Binding by Globular Proteins and Intact Tissues

Abstract

Improved technics have been developed for near infrared studies of water binding to globular proteins and in intact cells or tissues. These include the construction of a cylindrical absorption cell which is of variable path length and which can be re-opened for sample dehydration or re-closed for subsequent scans. A matrix composed of copolymers of methacrylic acid and diethylaminoethyl methacrylate, along with agarose, is utilized in order to hold globular or nongelling proteins in the form of uniform, transparent films when water is removed. Corrections have been made for the scattering of light by the samples by means of a particular opal material, in conjunction with a spectrophotometer with a high intensity source. Results which have been obtained with serum albumin and with intact tissues are presented. The spectra appear to provide sufficient resolution and accuracy for analytical studies, and for the detection of differences between bulk and protein bound forms of water. As far as we are aware, spectra with water difference curves through the near infrared, of intact tissues, with comparable resolution have not previously been published.