B3LYP calculations on bishomoaromaticity in substituted semibullvalenes*

B3LYP/6‐31G* calculations on the degenerate rearrangements of substituted semibullvalenes spuriously predict the relative enthalpies of the bishomoaromatic TSs to be lower than the experimental values. However, the calculations do make the useful and experimentally testable prediction that the two cyano and two phenyl substituents in 2,6‐dicyano‐4,8‐diphenylsemibullvalene ( 9d ) are more likely than four cyano substituents in 2,4,6,8‐tetracyanosemibullvalene ( 9f ) or the four phenyl substituents in 2,4,6,8‐tetraphenylsemibullvalene ( 9g ) to produce a semibullvalene that has a bishomoaromatic equilibrium geometry in the gas phase. The major reason for the surprising finding that 9d is more likely to be bishomoaromatic than 9g is shown to be steric interactions between the phenyl groups at C‐2 and C‐8 and at C‐4 and C‐6 in bishomoaromatic structure 10g . These interactions inhibit the conjugative stabilization of 10g ; but they are absent in bishomoaromatic structure 10d , where cyano groups replace the phenyl groups at C‐2 and C‐6 in 10g . © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1565–1573, 2001     

Activation of heat shock protein 70 promoter with meso-tetrahydroxyphenyl chlorin photodynamic therapy reported by green fluorescent protein in vitro and in vivo

Cellular responses to photodynamic therapy (PDT) include induction of heat shock proteins (HSP). We examined meso-tetrahydroxyphenyl chlorin (mTHPC) PDT-mediated HSP activation in EMT6 cells stably transfected with a plasmid containing the gene for green fluorescent protein (GFP) driven by an hsp70 promoter. mTHPC incubation induced concentration-dependent GFP expression. Irradiation of cells exposed to a sensitizer concentration that induced a slight increase in GFP and no loss of cell viability resulted in fluence-dependent GFP accumulation. In response to drug only and to PDT, GFP levels increased to a maximum of four- to five-fold above control levels with increasing drug or fluence and then decreased at higher doses. A trypan blue-exclusion assay confirmed that decreased GFP levels in both cases were due to a loss of cell viability. For initial evaluation in vivo, HSP70/ GFP-transfected EMT6 tumors were grown in BALB/c mice and subjected to mTHPC-PDT with a fluence of 1 J/cm2. Six hours after PDT, GFP fluorescence was imaged in these tumors through the intact skin in vivo. These results indicate that sublethal doses of mTHPC-PDT stimulate GFP expression under the control of an hsp70 promoter and illustrate the potential of noninvasively monitoring reporter protein fluorescence as a measure of molecular response to PDT.     

Model studies of colloidal silica precipitation using biosilica extracts from<Emphasis Type="Italic"> Equisetum telmateia</Emphasis>

Structural materials containing silicon are produced in single celled organisms through to higher plants and animals. Hydrated amorphous silica is a colloidal mineral of infinite functionality that is formed into structures with microscopic and macroscopic form. Proteins and proteoglycans are suggested to play a critical role in the catalysis of silica polycondensation and in structure direction during the formation of these magnificent structures. This article extends knowledge on the effect of protein containing biosilica extracts from Equisetum telmateia on the kinetics of silica formation and structure regulation. Utilising potassium silicon catecholate as the source of soluble silicon, bioextracts obtained from plant silica by dissolution of the siliceous phase with aqueous HF following extensive acid digestion of the plant cell wall were found to modify the kinetic rate constants for the formation of small silicic acid oligomers under circumneutral pH conditions and to modify the solubility of silicic acid in solution. Addition of the bioextracts at ca. 1 wt% to the reaction medium reduced the sizes and range of sizes of the fundamental silica particles formed and led to the formation of crystalline polymorphs of silica under conditions of ca. neutral pH, room temperature and in the absence of multiply charged cations, conditions assumed to be relevant to the biological mineralization environment. The ability of biological organisms to regulate the formation of silica structures with prevention of crystallinity is discussed as are the implications of this study in terms of the generation of new materials with specific form and function for industrial application.     

Hasse invariants for Hilbert modular varieties

Given a totally real fieldL of degreeg, we constructg Hasse invariants on Hilbert modular varieties in characteristicp and characterize their divisors. We show that these divisors give the type stratification defined by the action of on theα _p -elementary subgroup. Under certain conditions, involving special values of zeta functions, the product of these Hasse invariants is the reduction of an Eisenstein series of weightp−1