Reference

Study on the retrogradation of starch

Study on the retrogradation of starch. I. Particle size and its distribution of amylose retrograded from aqueous solutions. Kitamura, Shinichi; Yoneda, Susumu; Kuge, Takashi (Dep. Agric. Chem., Kyoto Prefect. Univ., Kyoto 606, Japan). Carbohydr. Polym., 4(2), 127-36 (English) 1984. CODEN: CAPOD8. DOCUMENT TYPE: Journal CA Section: 17 (Food and Feed Chemistry) The morphol. features of amylose [9005-82-7] ppts., esp. the particle size and size distribution, during retrogradation have been investigated using SEM. The retrograded amyloses consisted of particles with a surprising uniformity in size, and the vol. of each particle increased proportionally with the degree of retrogradation. These facts suggest that the retrogradation of amylose proceeds via a nucleation process, which is complete within a short time after the onset of retrogradation; this is then followed by growth of the nuclei. At a given percentage of retrogradation, the particle vol. 7447-40-7 and 9005-82-7 which are cas registry numbers of substances are two of reagents here. increased with increasing concn. of KCl in the soln. The redn. in the rate of retrogradation induced by KCl may thus be attributed to a decrease in the no. of nuclei produced in the initial stage. .

Nonequilibration of membrane-associated protons with the internal aqueous space in dark-maintained chloroplast thylakoids

Nonequilibration of membrane-associated protons with the internal aqueous space in dark-maintained chloroplast thylakoids. Laszlo, Joseph A.; Baker, Gary M.; Dilley, Richard A. (Dep. Biol. Sci., Purdue Univ., West Lafayette, IN 47907, USA). J. Bioenerg. Biomembr., 16(1), 37-51 (English) 1984. CODEN: JBBID4. ISSN: 0145-479X. DOCUMENT TYPE: Journal CA Section: 11 (Plant Biochemistry) Isolated spinach thylakoids retain a slowly equilibrating pool of protons in the dark which are predominantly bound to buffering groups, probably amines, with low pKa values. The effects of permeant buffers, salts, sucrose, and uncouplers on the retention of the proton pool were measured. Ac2O, which reacts with neutral primary amine groups, was used to det. the protonation state of the amine buffering groups. It was previously shown that the extent of inhibition of photosystem II water-oxidizing capacity by Ac2O and the increase in derivatization by Ac2O are proportional to, and dependent on, the deprotonated state of the amine buffering pool. Therefore, Ac2O inhibition of water oxidn. 7447-40-7 and 28380-24-7 are cas registry numbers of chemicals which are used as reagents here. activity may be used as a measure of the protonation state of the amine buffering pool. By this method it is inferred that protons, in a metastable state, were retained by membranes suspended in high pH buffer for several hours in the dark. When both the internal and external aq. phases were equilibrated with pH 8.8 buffer, the proton pool was released only upon addn. of a protonophore. The osmotic strength of the suspension buffer affected uncoupler-induced proton release, whereas ionic strength had little influence. The Ac2O-sensitive buffering group(s) of the water-oxidizing app. had an apparent pKa of 7.8. It appears that protein buffering groups reside either within the membrane matrix or in proteins at the membrane surface, not in equil. with the bulk aq. phases, and are responsible for the retention of the proton pool in dark-maintained chloroplasts. .