Assessment of major carcinogens and alkaloids in the tobacco and mainstream smoke of USSR cigarettes.

Tobacco and mainstream smoke of USSR cigarettes were analyzed for carcinogens. The pH values of suspensions of the tobacco (5.4-5.6) and the nitrate content of the tobaccos (0.4-1.7%) were as expected for flue-cured and sun-cured tobaccos and mixtures thereof. The nicotine levels of the cigarette tobaccos (0.76-0.94%) and total alkaloid content (0.85-1.08%) were relatively low compared with tobaccos used in Western European and US cigarettes. The concentrations of tobacco-specific N-nitrosamines in the cigarette tobaccos were also low (N'-nitrosonornicotine 0.36-0.85 microgram/g) compared with those in bright, oriental and blended cigarette tobaccos in Western countries (0.3-19 microgram/g). The 2 non-filter and 4 filter cigarettes from the USSR had slow burning rates and yielded 14.0-16.7 puffs/cigarette, while puff yields for commercial cigarettes in Western countries average less than or equal to 11 puffs/cigarette. Consequently, tar and benzo(a)pyrene yields in the smoke of all cigarettes as well as nitrosamine yields were high, especially in the smoke of the filter cigarettes. It appears that an increase in the burning rates of these cigarettes should lead to lower smoke yields.

Structural basis and dynamics of the fiber-to-crystal transition of sickle cell hemoglobin.

The kinetics of the assembly of structurally distinct, polymeric aggregates constituting the fiber-to-crystal transition of sickle cell hemoglobin in slowly stirred, deoxygenated solutions has been studied with the use of electron microscopy as a function of pH, as a function of the crystal structures of mutant forms of human deoxyhemoglobins employed as nucleating seeds, and as a function of hemoglobin S chemically modified at the Cys F9 (beta 93) position. The temporal order of appearance of fibers of approximately 210 A diameter, bundles of aligned fibers, macrofibers of greater than or equal to 650 A diameter, and microcrystals is observed. Microscopic fragments of end-stage crystals formed under slowly stirred conditions and introduced as nucleating seeds enhance the rate of crystallization only when added prior to the formation of large bundles of aligned fibers, while microscopic seed crystals added after the formation of bundles of aligned fibers do not alter the rate of crystallization. Over the pH range 6.3 to 7.1, the presence of macrofibers does not influence modulation of the kinetics of the transition with seed crystal fragments. Microscopic seed crystals of deoxyhemoglobin S and deoxyhemoglobin C formed under acidic conditions (pH less than 6.5) have a comparable influence on the kinetics of the fiber-to-crystal transition to that of end-stage crystals. Microscopic seed crystals of deoxyhemoglobin C formed under alkaline conditions (pH greater than 6.5) enhance the formation of macrofibers but do not alter the rate of crystallization. Under conditions associated with enhanced formation of macrofibers, metastable microscopic crystals having axial periodicities of approximately 64 A and approximately 210 A are observed in the intermediate phase of the transition, while end-stage crystals have axial unit cell dimensions identical to those of deoxyhemoglobin S crystallized from polyethylene glycol solutions of pH less than 6.5. Although the metastable crystals may arise from fragments of macrofibers, it is shown that they cannot be transformed directly into end-stage crystals under slowly stirred conditions without undergoing dissolution. These results stipulate that the pathway of the fiber-to-crystal transition proceeds according to the reaction: (Formula: see text) wherein the rate-limiting step is the alignment of fibers into large bundles, and macrofibers are not an intermediate of the fiber-to-crystal transition.(ABSTRACT TRUNCATED AT 400 WORDS)