Two-level system with a thermally fluctuating transfer matrix element: Application to the problem of DNA charge transfer

Charge transfer along the base-pair stack in DNA is modeled in terms of thermally-assisted tunneling between adjacent base pairs. Central to our approach is the notion that tunneling between fluctuating pairs is rate-limited by the requirement of their optimal alignment. We focus on this aspect of the process by modeling two adjacent base pairs in terms of a classical damped oscillator subject to thermal fluctuations as described by a Fokker-Planck equation. We find that the process is characterized by two time scales, a result that is in accord with experimental findings.Comment: original file is revtex4, 10 pages, three eps figure

Bromophycolides C-I from the Fijian red alga Callophycus serratu

Bromophycolides C-I (1-7) were isolated from extracts of the Fijian red alga Callophycus serratus and identified by NMR and mass spectral techniques. These novel natural products share a carbon skeleton and biosynthetic origin with previously identified bromophycolides A (8) and B (9), which form a rare group of diterpene-benzoate macrolides. Bromophycolides C-I (1-7) displayed modest antineoplastic activity against a range of human tumor cell lines

Relationship of cytokines and cytokine signaling to immunodeficiency disorders in the mouse

The contributions of cytokines to the development and progression of disease in a mouse model of retrovirus-induced immunodeficiency (MAIDS) are controversial. Some studies have indicated an etiologic role for type 2 cytokines, while others have emphasized the importance of type 1 cytokines. We have used mice deficient in expression of IL-4, IL-10, IL-4 and IL-10, IFN-<FONT FACE="Symbol">g</font>, or ICSBP - a transcriptional protein involved in IFN signaling - to examine their contributions to this disorder. Our results demonstrate that expression of type 2 cytokines is an epiphenomenon of infection and that IFN-<FONT FACE="Symbol">g</font> is a driving force in disease progression. In addition, exogenously administered IL-12 prevents many manifestations of disease while blocking retrovirus expression. Interruption of the IFN signaling pathways in ICSBP-/- mice blocks induction of MAIDS. Predictably, ICSBP-deficient mice exhibit impaired responses to challenge with several other viruses. This immunodeficiency is associated with impaired production of IFN-<FONT FACE="Symbol">g</font> and IL-12. Unexpectedly, however, the ICSBP-/- mice also develop a syndrome with many similarities to chronic myelogenous leukemia in humans. The chronic phase of this disease is followed by a fatal blast crisis characterized by clonal expansions of undifferentiated cells. ICSBP is thus an important determinant of hematopoietic growth and differentiation as well as a prominent signaling molecule for IFN

Antineoplastic diterpene-benzoate macrolides from the Fijian red alga Callophycus serratus

Three diterpene-benzoate natural products, with novel carbon skeletons and an unusual proposed biosynthesis, were isolated from extracts of the Fijian red alga Callophycus serratus and identified by a combination of X-ray crystallographic, NMR, and mass spectral analyses. Bromophycolide A (1) displayed cytotoxicity against several human tumor cell lines via specific apoptotic cell death. This represents the first discovery of natural products incorporating a diterpene and benzoate skeleton into a macrolide system

Novel antineoplastic diterpene-benzoates from the Fijian red alga Callophycus serratus

Red macroalgae are well-known for the production of brominated metabolites, including terpenoids and phenols, yet some taxa within the Rhodophyta remain relatively unstudied. Herein, we report the discovery of unusual diterpene-benzoate natural products representing three novel carbon skeletons, from the red alga Callophycus serratus collected in Fiji. Included among the new compounds were 15- and 16-membered macrolides as well as non-macrocyclic diterpene-benzoic acid structural motifs, all apparently sharing the same 27-carbon biosynthetic precursor. Biological activities of these compounds included moderate antibacterial, antiviral, and antineoplastic effects via specific apoptotic cell death

Modal Tableau Systems with Blocking and Congruence Closure

International audienc