SynopsisA new .infrared ratio, a1372 om.-l/u~~ cm,-l, is proposed for measuring crystallinity in cellulosic materials. The advantage of this ratio over others which have been used is that it can be applied to both celluloses I and I1 and, therefore, to samples containing a mixed lattice. Two series of samples, encompassing a wide range of crystallinity, were prepared from highly crystalline celluloses I and 11. The infrared ratios of these samples were compared with crystallinity values from x-ray diffractograms and density measurements, and with accessibility data from moisture sorption. It was shown that the new infrared ratio ranks samples of both lattice types, as well as partly mercerized cottons, in the same order as do x-ray, density, and moisture sorption data. The correlation of the new infrared ratio with accessibility, derived from moisture regain, is better than with crystallinities from either x-ray or density measurements. Reasons for this are suggested.

Cell signaling that culminates in posttranslational modifications directs protein activity. Here we report how multiple Ca 2+ -dependent phosphorylation sites within the transcription activator Ets-1 act additively to produce graded DNA binding affinity. Nuclear magnetic resonance spectroscopic analyses show that phosphorylation shifts Ets-1 from a dynamic conformation poised to bind DNA to a well-folded inhibited state. These phosphates lie in an unstructured flexible region that functions as the allosteric effector of autoinhibition. Variable phosphorylation thus serves as a “rheostat” for cell signaling to fine-tune transcription at the level of DNA binding.