Phytochrome Control of Anthocyanin Biosynthesis in Tomato Seedlings: Analysis Using Photomorphogenic Mutants

Anthocyanin biosynthesis has been studied in hypocotyls and whole seedlings of tomato (Lycoperskon esculentum Mill.) wild types (WTs) and photomorphogenic mutants. In white light (WL)/dark (D) cycles the fri¹ mutant, deficient in phytochrome A (phyA), shows an enhancement of anthocyanin accumulation, whereas the tri¹ mutant, deficient in phytochrome Bl (phyBl) has a WT level of anthocyanin. Under pulses of red light (R) or R followed by far-red light (FR) given every 4 h, phyA is responsible for the non-R/FR reversible response, whereas phyBl is partially responsible for the R/FR reversible response. From R and blue light (B) pretreatment studies, B is most effective in increasing phytochrome responsiveness, whereas under R itself it appears to be dependent on the presence of phyBl. Anthocyanin biosynthesis during a 24 h period of monochromatic irradiation at different flu-ence rates of 4 day-old D-grown seedlings has been studied. At 660 nm the fluence rate-response relationships for induction of anthocyanin in the WT are similar, yet complex, showing a low fluence rate response (LFRR) and a fluence rate-dependent high irradiance response (HIR). The high-pigment-1 (hp-1) mutant exhibits a strong amplification of both the LFRR and HIR. The fri¹ mutant lacks the LFRR while retaining a normal HIR. In contrast, a transgenic tomato line overexpressing the oat PHYA3 gene shows a dramatic amplification of the LFRR. The tri¹ mutant, retains the LFRR but lacks the HIR, whereas the fri¹, tri¹ double mutant lacks both components. Only an LFRR is seen at 729 nm in WT; however, an appreciable HIR is observed at 704 nm, which is retained in the tri¹ mutant and is absent in the fri¹ mutant, indicating the labile phyA pool regulates this response component.     

On Ultrasmall Nanocrystals

Ultrasmall nanocrystals are a growing sub-class of traditional nanocrystals that exhibit new properties at diameters typically below 2 nm. In this review, we define what constitutes an ultrasmall nanoparticle while distinguishing between ultrasmall and magic-size nanoparticles. After a brief overview of ultrasmall nanoparticles, including ultrasmall gold clusters, our recent work is presented covering the optical properties, structure, and application of ultrasmall CdSe nanocrystals. This unique material has potential application in solid state lighting due to its balanced white emission. This section is followed by a discussion on the blurring boundary between what can be considered a nanoparticle and a molecule.     

Novel Inhibitors of Nicotinamide-N-Methyltransferase for the Treatment of Metabolic Disorders

Nicotinamide-N-methyltransferase (NNMT) is a cytosolic enzyme catalyzing the transfer of a methyl group from S-adenosyl-methionine (SAM) to nicotinamide (Nam). It is expressed in many tissues including the liver, adipose tissue, and skeletal muscle. Its expression in several cancer cell lines has been widely discussed in the literature, and recent work established a link between NNMT expression and metabolic diseases. Here we describe our approach to identify potent small molecule inhibitors of NNMT featuring different binding modes as elucidated by X-ray crystallographic studies.     

Evidence for C?Cl/C?Br⋅⋅⋅π Interactions as an Important Contribution to Protein–Ligand Binding Affinity

Attractive chlorine : Noncovalent interactions between chlorine or bromine atoms and aromatic rings in proteins open up a new method for the manipulation of molecular recognition. Substitution at distinct positions of two factor Xa inhibitors improves the free energy of binding by interaction with a tyrosine unit. The generality of this motif was underscored by multiple crystal structures as well as high‐level quantum chemical calculations (see picture).

     

A general ratio estimator and its application in model based inference

A general ratio estimator of a population total is proposed as an approximation to the estimator introduced by Srivastava (1985,Bull. Internat. Statist. Inst.,51(10.3), 1–16). This estimator incorporates additional information gathered during the survey in a new way. Statistical properties of the general ratio estimator are given and its relationship to the estimator proposed by Srivastava is explored. A special kind of general ratio estimator is suggested and it turns out to be very efficient in a simulation study when compared to several other commonly used estimators.The work of this author was supported by AFOSR grant #830080.     

Determination of beta-galactosidase activity in the intestinal tract of mice by ion-exchange high-performance liquid chromatography using epsilon-N-1-(1-deoxylactulosyl)-L-lysine as substrate

epsilon-N-1-(1-Deoxylactulosyl)-L-lysine was synthesized and used as a substrate to assay beta-galactosidase activity. epsilon-N-1-(1-Deoxylactulosyl)-L-lysine and its degradation product epsilon-N-1-(1-deoxyfructosyl)-L-lysine were detected by high-voltage paper electrophoresis and ion-exchange high-performance liquid chromatography. The beta-galactosidase activity in different parts of the intestinal tract of germ-free and control mice was determined and compared with a beta-galactosidase activity which degrades lactose at pH 8.5 and 5.0 and which corresponded with bacterial and host enzymatic activities, respectively.     

Modelling of the binding site of the human m1 muscarinic receptor: Experimental validation and refinement

Our model of the human m1 muscarinic receptor has been refined on the basis of the recently published projection map of bovine rhodopsin. The refined model has a slightly different helix arrangement, which reveals the presence of an extra hydrophobic pocket located between helices 3, 4 and 5. The interaction of series of agonists and antagonists with the m1 muscarinic receptor has been studied experimentally by site-directed mutagenesis. In order to account for the observed results, three-dimensional models of m1 ligands docked in the target receptor are proposed. Qualitatively, the obtained models are in good agreement with the experimental observations. Agonists and partial agonists have a relatively small size. They can bind to the same region of the receptor using, however, different anchoring receptor residues. Antagonists are usually larger molecules, filling almost completely the same pocket as agonists. They can usually produce much stronger interactions with aromatic residues. Experimental data combined with molecular modelling studies highlight how subtle and diverse receptor–ligand interactions could be.     

Rapid sample preparation method for the determination of chloramphenicol in swine muscle by high-performance liquid chromatography

A simple and rapid sample preparation method for the determination of chloramphenicol in swine muscle tissue at the 10 micrograms/kg level is described. The method comprises sonication-aided extraction with ethyl acetate, addition of hexane to the extract and cleaning up and concentration of the extract on a small column packed with silica gel. Analysis was performed by high-performance liquid chromatography on a ChromSep column with ChromSpher C8 using acetonitrile-sodium acetate buffer as the mobile phase. Detection was performed at 280 nm. Mean recoveries from spiked muscle samples were 79 +/- 3% (10-50 micrograms/kg). The distribution of chloramphenicol in different muscle and fatty tissues from a pig to which a single dose of chloramphenicol was administered was also investigated.