Facile Chemoselective Strategy toward Capturing Sphingoid Bases by a Unique Glutaraldehyde-Functionalized Resin.

Sphingoid bases, which have a 2-amino-1,3-diol common functional group, are the structural backbone units of all sphingolipids. Recently, much attention has been focused on sphingoid bases because of their potentially beneficial bioactivities toward various cancer cells as well as their dietary interest. However, low abundance and the handling complexity caused by their amphiphilic character led to very limited research on them.

Stereochemical Study of Sphingosine by Vibrational Circular Dichroism.

Vibrational circular dichroism (VCD) was first applied to the stereochemical analysis of sphingosine. VCD patterns derived from the C═C stretch as well as other mid-infrared (IR) regions were practical markers to discriminate all the stereoisomers of intact sphingosine. Glutaraldehyde was found as an excellent derivatizing reagent for sphingosine which improves its solubility in VCD-friendly nonpolar solvents such as chloroform and enhances the VCD intensities by forming a rigid cyclized structure.

What Is the True Structure of D609, a Widely Used Lipid Related Enzyme Inhibitor?

D609 (1) has been used as a lipid-related enzyme inhibitor during the past three decades. Although it has eight possible stereoisomers, no systematic research considering its chirality has been performed. In this paper, eight possible chiral alcohols as direct precursors of D609 were synthesized, and their stereochemistries were elucidated by a vibrational circular dichroism (VCD) technique.

Highly efficient preparation of sphingoid bases from glucosylceramides by chemoenzymatic method.

Sphingoid base derivatives have attracted increasing attention as promising chemotherapeutic candidates against lifestyle diseases such as diabetes and cancer. Natural sphingoid bases can be a potential resource instead of those derived by time-consuming total organic synthesis. In particular, glucosylceramides (GlcCers) in food plants are enriched sources of sphingoid bases, differing from those of animals.

Electronic transitions and heterogeneity of the bacteriophytochrome Pr absorption band: An angle balanced polarization resolved femtosecond VIS pump-IR probe study.

Photoisomerization of biliverdin (BV) chromophore triggers the photoresponse in native Agp1 bacteriophytochrome. We discuss heterogeneity in phytochrome Pr form to account for the shape of the absorption profile. We investigated different regions of the absorption profile by angle balanced polarization resolved femtosecond VIS pump-IR probe spectroscopy.

Fluorescence of phytochrome adducts with synthetic locked chromophores.

We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive.

The use of synthetic linear tetrapyrroles to probe the verdin sites of human biliverdin-IXalpha reductase and human biliverdin-IXbeta reductase.

Many vertebrate species express two enzymes that are capable of catalysing the reduction of various isomers of biliverdin. Biliverdin-IXalpha reductase (BVR-A) is most active with its physiological substrate biliverdin-IXalpha, but can also reduce the three other biliverdin isomers IXbeta, IXdelta and IXgamma. Biliverdin-IXbeta reductase (BVR-B) catalyses the reduction of only the IXbeta, IXdelta and IXgamma isomers of biliverdin.

Assembly of synthetic locked chromophores with agrobacterium phytochromes Agp1 and Agp2.

Phytochromes are photoreceptors with a bilin chromophore in which light triggers the conversion between the red-absorbing form Pr and the far-red-absorbing form Pfr. Agrobacterium tumefaciens has two phytochromes, Agp1 and Agp2, with antagonistic properties: in darkness, Agp1 converts slowly from Pfr to Pr, whereas Agp2 converts slowly from Pr to Pfr. In a previous study, we have assembled Agp1 with synthetic locked chromophores 15Za, 15Zs, 15Ea, and 15Es in which the C15=C16 double bond is fixed in either the E or Z configuration and the C14-C15 single bond is fixed in either the syn (s) or anti (a) conformation.

Crystallization and preliminary X-ray crystallographic analysis of the N-terminal photosensory module of phytochrome Agp1, a biliverdin-binding photoreceptor from Agrobacterium tumefaciens.

Phytochromes are photochromic photoreceptors with a bilin chromophore that have been found in plants and bacteria. Typical bacterial phytochromes are composed of an N-terminal photosensory chromophore module and a C-terminal protein kinase. The former contains the chromophore, which allows phytochromes to adopt the two interconvertible spectral forms, Pr and Pfr.

Sterically locked synthetic bilin derivatives and phytochrome Agp1 from Agrobacterium tumefaciens form photoinsensitive Pr- and Pfr-like adducts.

Phytochrome photoreceptors undergo reversible photoconversion between the red-absorbing form, Pr, and the far-red-absorbing form, Pfr. The first step in the conversion from Pr to Pfr is a Z to E isomerization around the C15=C16 double bond of the bilin chromophore. We prepared four synthetic biliverdin (BV) derivatives in which rings C and D are sterically locked by cyclizing with an additional carbon chain.