Katsumi Ajisaka

Modification of human hemoglobin with polyethylene glycol: A new candidate for blood substitute

Human hemoglobin was modified with polyethylene glycols. The conjugates exhibited P50 values of 10–15 mmHg, those are enough to deliver oxygen from the lungs to tissues. The most remarkable characteristic is their long half disappearance time from the circulation. The longest half disappearance time of these derivatives is about 180 minutes in contrast to 45 minutes of free hemoglobin. The half disappearance time shows a good corelation not to molecular weight but to the effective molecular size, which is determined by the elution time of HPLC on a gel permeation column.

Hemoglobin-inulin conjugate as an oxygen carrying blood substitute.

Pyridoxylated hemoglobin was modified with the activated ester of inulin. From the oxygen equilibrium curve, this conjugate was estimated to have about fivefold oxygen carrying capacity compared with a free hemoglobin. The half disappearance time of this conjugate in the circulation of a rat was 21 hours in contrast to 3 hours of a free hemoglobin. The oncotic pressure and the viscosity can be adjusted nearly equal to those of whole blood. This conjugate can be concluded to have sufficient properties for use as a blood substitute.

In situ analysis of the microbial fermentation process by natural abundance 13C and 31P NMR spectroscopy. Production of adenosine-5′-triphosphate from adenosine

The application of 13C NMR spectroscopy to in situ analysis of the complex microbial metabolites has been reported by Eakin et al. [l] . They studied the fate of [ 1 -13 C] glucose on being fed to yeast cells, Candida utilis, by monitoring the 13C NMR spectra of metabolites without separating them from the incubation broth. Use of I-13C-enriched substrate, as has been pointed out by Eakin et al. [l] , would allow one to use a substrate concentration lower than several millimolar for its increased NMR sensitivity, although usual microbial fermentations, which are carried out in both laboratories and industry, use much higher substrate concentrations. The r3C enrichment may still be essential to study the transient metabolites which might exist in the fermentation process only for a short period of time compared to the duration to obtain the r3C NMR spectra of metabolites at natural 13C abundance of 1 .l%, or to search for the metabolites which might exist at very low concentration, either in intraor extracellular medium. Despite the merit of higher NMR sensitivity described above use of the r3C-enriched substrates in analyzing microbial reactions has obvious drawbacks. As only the enriched portion of the carbons in the metabolites can be detected, unexpected metabolites in the broth may hardly be characterized. The metabolites, by the same reason, which bear no carbons from the enriched part of the substrate may be overlooked.

Conformation of 1- and 3-deazaadenosines in solution as studied by 1H nuclear magnetic resonance spectroscopy (1)

Abstract 1H nuclear magnetic resonance spectra of 1 - (II) and 3-deazaadenosines (III) together with adenosine (I) in dimethylsulfoxide have been examined. Features of coupling constants indicate that the furanose rings of I, II, and III have similar conformational preferences and that conformations about the 4′-C–5′-C bond are preferentially gauche-gauche . Nuclear Overhauser effect and spin-lattice relaxation-time measurements demonstrate that II predominantly adopts the syn -conformation similar to that of I, whereas that of III has a greater anti (freely rotating) component. The results suggest that the syn -conformation in II as well as I is stabilized presumably through a hydrogen bond between the 3-N and 5′-hydroxyl group.