Abstract:It is the aim of this article to review the major theories of polymer crystallization since up to now we still have not completely comprehended the underlying mechanism in a unified framework. A lack of paradigm is an indicator of immaturity of the field itself; thus, the fundamental issue of polymer crystallization remains unsolved. This paper provides an understanding of the basic hypothesis, as well as relevant physical implications and consequences of each theory without too much bias. We try to present the essential aspects of the major theories, and intuitive physical arguments over rigorously mathematical calculations are highlighted. In addition, a detailed comparison of various theories will be made in a logical and self-contained fashion. Our personal view of the existing theories is presented as well, aiming to inspire further open discussions. We expect that new theories based on the framework of kinetics with direct consideration of long-range multi-body correlation will help solve the remaining problems in the field of polymer crystallization.

Niacin is an effective agent for raising HDL, but its cellular target sites are largely unknown. We examined effects of niacin on the surface expression of ATP synthase b chain, a newly described HDL/apolipoprotein A-I (apoA-I) receptor for HDL endocytosis, in HepG2 cells. A significant amount of immunodetectable b chain was observed on the surface of HepG2 cells, which was competitively displaced by apoA-I. Niacin treatment reduced the surface expression of b chain in HepG2 cells by ?27%, and decreased 125 I-labeled HDL uptake up to ?35%. However, nicotinamide, a niacin metabolite that does not have clinical lipid effects, exhibited weaker inhibition on the b chain cell surface expression, and failed to show inhibitory action on 125 I-labeled HDL uptake. Furthermore, anti-b chain antibody significantly reduced 125 I-labeled HDL uptake and abolished the inhibitory effect of niacin. Niacin did not change b chain mRNA expression. These data suggest that niacin inhibits cell surface expression of the ATP synthase b chain, leading to reduced hepatic removal of HDL protein, thus implicating a potential cellular target for niacin action to raise HDL.-Zhang, L-H., V. S. Kamanna, M. C. Zhang, and M. L. Kashyap. Niacin inhibits surface expression of ATP synthase b chain in HepG2 cells: implications for raising HDL.

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