The evaluation of acute toxicity,antimicrobial activity of 1‐phenyl‐5‐p‐tolyl‐1H‐1, 2, 3‐triazole,and binding to human serum albumin

1‐Phenyl‐5‐p‐tolyl‐1H‐1, 2, 3‐triazole (PPTA) was a synthesized compound. The result of acute toxicities to mice of PPTA by intragastric administration indicated that PPTA did not produce any significant acute toxic effect on Kunming strain mice. It exhibited the various potent inhibitory activities against two kinds of bananas pathogenic bacteria, black sigatoka and freckle, when compared with that of control drugs and the inhibitory rates were up to 64.14% and 43.46%, respectively, with the same concentration of 7.06 mM. The interaction of PPTA with human serum albumin (HSA) was studied using fluorescence polarization, absorption spectra, 3D fluorescence, and synchronous spectra in combination with quantum chemistry and molecular modeling. Multiple modes of interaction between PPTA and HSA were suggested to stabilize the PPTA–HSA complex, based on thermodynamic data and molecular modeling. Binding of PPTA to HSA induced perturbation in the microenvironment around HSA as well as secondary structural changes in the protein.     

Osmotic second virial cross‐coefficient measurements for binary combination of lysozyme,ovalbumin, and α‐amylase in salt solutions

Interactions measurement is a valuable tool to predict equilibrium phase separation of a desired protein in the presence of unwanted macromolecules. In this study, cross‐interactions were measured as the osmotic second virial cross‐coefficients (B₂₃) for the three binary protein systems involving lysozyme, ovalbumin, and α‐amylase in salt solutions (sodium chloride and ammonium sulfate). They were correlated with solubility for the binary protein mixtures. The cross‐interaction behavior at different salt concentrations was interpreted by either electrostatic or hydrophobic interaction forces. At low salt concentrations, the protein surface charge dominates cross‐interaction behavior as a function of pH. With added ovalbumin, the lysozyme solubility decreased linearly at low salt concentration in sodium chloride and increased at high salt concentration in ammonium sulfate. The B₂₃ value was found to be proportional to the slope of the lysozyme solubility against ovalbumin concentration and the correlation was explained by preferential interaction theory. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1203–1211, 2013     

LEW3, encoding a putative α‐1,2‐mannosyltransferase (ALG11) in N‐linked glycoprotein,plays vital roles in cell‐wall biosynthesis and the abiotic stress response in Arabidopsis thaliana

N‐linked glycosylation is an essential protein modification that helps protein folding, trafficking and translocation in eukaryotic systems. The initial process for N‐linked glycosylation shares a common pathway with assembly of a dolichol‐linked core oligosaccharide. Here we characterize a new Arabidopsis thaliana mutant lew3 (leaf wilting 3), which has a defect in an α‐1,2‐mannosyltransferase, a homolog of ALG11 in yeast, that transfers mannose to the dolichol‐linked core oligosaccharide in the last two steps on the cytosolic face of the ER in N‐glycan precursor synthesis. LEW3 is localized to the ER membrane and expressed throughout the plant. Mutation of LEW3 caused low‐level accumulation of Man₃GlcNAc₂ and Man₄GlcNAc₂ glycans, structures that are seldom detected in wild‐type plants. In addition, the lew3 mutant has low levels of normal high‐mannose‐type glycans, but increased levels of complex‐type glycans. The lew3 mutant showed abnormal developmental phenotypes, reduced fertility, impaired cellulose synthesis, abnormal primary cell walls, and xylem collapse due to disturbance of the secondary cell walls. lew3 mutants were more sensitive to osmotic stress and abscisic acid (ABA) treatment. Protein N‐glycosylation was reduced and the unfolded protein response was more activated by osmotic stress and ABA treatment in the lew3 mutant than in the wild‐type. These results demonstrate that protein N‐glycosylation plays crucial roles in plant development and the response to abiotic stresses.     

Structure of 6‐diazo‐5‐oxo‐norleucine‐bound human gamma‐glutamyl transpeptidase 1, a novel mechanism of inactivation

Intense efforts are underway to identify inhibitors of the enzyme gamma‐glutamyl transpeptidase 1 (GGT1) which cleaves extracellular gamma‐glutamyl compounds and contributes to the pathology of asthma, reperfusion injury and cancer. The glutamate analog, 6‐diazo‐5‐oxo‐norleucine (DON), inhibits GGT1. DON also inhibits many essential glutamine metabolizing enzymes rendering it too toxic for use in the clinic as a GGT1 inhibitor. We investigated the molecular mechanism of human GGT1 (hGGT1) inhibition by DON to determine possible strategies for increasing its specificity for hGGT1. DON is an irreversible inhibitor of hGGT1. The second order rate constant of inactivation was 0.052 mM ^?1 min^?1 and the K _i was 2.7 ± 0.7 mM . The crystal structure of DON‐inactivated hGGT1 contained a molecule of DON without the diazo‐nitrogen atoms in the active site. The overall structure of the hGGT1‐DON complex resembled the structure of the apo‐enzyme; however, shifts were detected in the loop forming the oxyanion hole and elements of the main chain that form the entrance to the active site. The structure of hGGT1‐DON complex revealed two covalent bonds between the enzyme and inhibitor which were part of a six membered ring. The ring included the OG atom of Thr381, the reactive nucleophile of hGGT1 and the α‐amine of Thr381. The structure of DON‐bound hGGT1 has led to the discovery of a new mechanism of inactivation by DON that differs from its inactivation of other glutamine metabolizing enzymes, and insight into the activation of the catalytic nucleophile that initiates the hGGT1 reaction.     

Targeting and post‐translational processing of human α1‐antichymotrypsin in BY‐2 tobacco cultured cells†

The post‐translational processing of human α₁‐antichymotrypsin (AACT) in Bright Yellow‐2 (BY‐2) tobacco cells was assessed in relation to the cellular compartment targeted for accumulation. As determined by pulse‐chase labelling experiments and immunofluorescence microscopy, AACT sent to the vacuole or the endoplasmic reticulum (ER) was found mainly in the culture medium, similar to a secreted form targeted to the apoplast. Unexpectedly, AACT expressed in the cytosol was found in the nucleus under a stable, non‐glycosylated form, in contrast with secreted variants undergoing multiple post‐translational modifications during their transit through the secretory pathway. All secreted forms of AACT were N‐glycosylated, with the presence of complex glycans as observed naturally on human AACT. Proteolytic trimming was also observed for all secreted variants, both during their intracellular transit and after their secretion in the culture medium. Overall, the targeting of human AACT to different compartments of BY‐2 tobacco cells led to the production of two protein products: (i) a stable, non‐glycosylated protein accumulated in the nucleus; and (ii) a heterogeneous mixture of secreted variants resulting from post‐translational N‐glycosylation and proteolytic processing. Overall, these data suggest that AACT is sensitive to resident proteases in the ER, the Golgi and/or the apoplast, and that the production of intact AACT in the plant secretory pathway will require innovative approaches to protect its structural integrity in vivo. Studies are now needed to assess the activity of the different AACT variants, and to identify the molecular determinants for the nuclear localization of AACT expressed in the cytosol.     

Resolution of 1‐n‐Butyl‐3‐Methyl‐3‐Phospholene 1‐Oxide With TADDOL Derivatives and Calcium Salts of O,O'‐Dibenzoyl‐(2R,3R)‐ or O,O'‐di‐p‐Toluoyl‐(2R,3R)‐tartaric Acid

The resolution methods applying (?)‐(4R,5R)‐4,5‐bis(diphenylhydroxymethyl)‐2,2‐dimethyldioxolane (“TADDOL”), (?)‐(2R,3R)‐α,α,α',α'‐tetraphenyl‐1,4‐dioxaspiro[4.5]decan‐2,3‐dimethanol (“spiro‐TADDOL”), as well as the acidic and neutral Ca²⁺ salts of (?)‐O,O'‐dibenzoyl‐ and (?)‐O,O'‐di‐p‐toluoyl‐(2R,3R)‐tartaric acid were extended for the preparation of 1‐n‐butyl‐3‐methyl‐3‐phospholene 1‐oxide in optically active form. In one case, the intermediate diastereomeric complex could be identified by single‐crystal X‐ray analysis. The absolute P‐configuration of the enantiomers of the phospholene oxide was also determined by comparing the experimentally obtained and calculated CD spectra. Chirality 26:174–182, 2014. © 2014 Wiley Periodicals, Inc.     

5α‐Androst‐16‐en‐3α‐ol β‐D‐Glucuronide,Precursor of 5α‐Androst‐16‐en‐3α‐ol in Human Sweat

5α‐Androst‐16‐en‐3α‐ol (α‐androstenol) is an important contributor to human axilla sweat odor. It is assumed that α‐andostenol is excreted from the apocrine glands via a H₂O‐soluble conjugate, and this precursor was formally characterized in this study for the first time in human sweat. The possible H₂O‐soluble precursors, sulfate and glucuronide derivatives, were synthesized as analytical standards, i.e., α‐androstenol, β‐androstenol sulfates, 5α‐androsta‐5,16‐dien‐3β‐ol (β‐androstadienol) sulfate, α‐androstenol β‐glucuronide, α‐androstenol α‐glucuronide, β‐androstadienol β‐glucuronide, and α‐androstenol β‐glucuronide furanose. The occurrence of α‐androstenol β‐glucuronide was established by ultra performance liquid chromatography (UPLC)/MS (heated electrospray ionization (HESI)) in negative‐ion mode in pooled human sweat, containing eccrine and apocrine secretions and collected from 25 female and 24 male underarms. Its concentration was of 79 ng/ml in female secretions and 241 ng/ml in male secretions. The release of α‐androstenol was observed after incubation of the sterile human sweat or α‐androstenol β‐glucuronide with a commercial glucuronidase enzyme, the urine‐isolated bacteria Streptococcus agalactiae, and the skin bacteria Staphylococcus warneri DSM 20316, Staphylococcus haemolyticus DSM 20263, and Propionibacterium acnes ATCC 6919, reported to have β‐glucuronidase activities. We demonstrated that if α‐ and β‐androstenols and androstadienol sulfates were present in human sweat, their concentrations would be too low to be considered as potential precursors of malodors; therefore, the H₂O‐soluble precursor of α‐androstenol in apocrine secretion should be a β‐glucuronide.     

Improved fruit α‐tocopherol,carotenoid, squalene and phytosterol contents through manipulation of Brassica juncea 3‐HYDROXY‐3‐METHYLGLUTARYL‐COA SYNTHASE1 in transgenic tomato

3‐Hydroxy‐3‐methylglutaryl‐coenzyme A synthase (HMGS) in the mevalonate (MVA) pathway generates isoprenoids including phytosterols. Dietary phytosterols are important because they can lower blood cholesterol levels. Previously, the overexpression of Brassica juncea wild‐type (wt) and mutant (S359A) BjHMGS1 in Arabidopsis up‐regulated several genes in sterol biosynthesis and increased sterol content. Recombinant S359A had earlier displayed a 10‐fold higher in vitro enzyme activity. Furthermore, tobacco HMGS overexpressors (OEs) exhibited improved sterol content, plant growth and seed yield. Increased growth and seed yield in tobacco OE‐S359A over OE‐wtBjHMGS1 coincided with elevations in NtSQS expression and sterol content. Herein, the overexpression of wt and mutant (S359A) BjHMGS1 in a crop plant, tomato (Solanum lycopersicum), caused an accumulation of MVA‐derived squalene and phytosterols, as well as methylerythritol phosphate (MEP)‐derived α‐tocopherol (vitamin E) and carotenoids, which are important to human health as antioxidants. In tomato HMGS‐OE seedlings, genes associated with the biosyntheses of C10, C15 and C20 universal precursors of isoprenoids, phytosterols, brassinosteroids, dolichols, methylerythritol phosphate, carotenoid and vitamin E were up‐regulated. In OE‐S359A tomato fruits, increased squalene and phytosterol contents over OE‐wtBjHMGS1 were attributed to heightened SlHMGR2, SlFPS1, SlSQS and SlCYP710A11 expression. In both tomato OE‐wtBjHMGS1 and OE‐S359A fruits, the up‐regulation of SlGPS and SlGGPPS1 in the MEP pathway that led to α‐tocopherol and carotenoid accumulation indicated cross‐talk between the MVA and MEP pathways. Taken together, the manipulation of BjHMGS1 represents a promising strategy to simultaneously elevate health‐promoting squalene, phytosterols, α‐tocopherol and carotenoids in tomato, an edible fruit.     

Solution structures of polcalcin Phl p 7 in three ligation states: Apo‐, hemi‐Mg2+‐bound,and fully Ca2+‐bound

Polcalcins are small EF‐hand proteins believed to assist in regulating pollen‐tube growth. Phl p 7, from timothy grass (Phleum pratense), crystallizes as a domain‐swapped dimer at low pH. This study describes the solution structures of the recombinant protein in buffered saline at pH 6.0, containing either 5.0 mM EDTA, 5.0 mM Mg²⁺, or 100 μM Ca²⁺. Phl p 7 is monomeric in all three ligation states. In the apo‐form, both EF‐hand motifs reside in the closed conformation, with roughly antiparallel N‐ and C‐terminal helical segments. In 5.0 mM Mg²⁺, the divalent ion is bound by EF‐hand 2, perturbing interhelical angles and imposing more regular helical structure. The structure of Ca²⁺‐bound Phl p 7 resembles that previously reported for Bet v 4—likewise exposing apolar surface to the solvent. Occluded in the apo‐ and Mg²⁺‐bound forms, this surface presumably provides the docking site for Phl p 7 targets. Unlike Bet v 4, EF‐hand 2 in Phl p 7 includes five potential anionic ligands, due to replacement of the consensus serine residue at –x (residue 55 in Phl p 7) with aspartate. In the Phl p 7 crystal structure, D55 functions as a helix cap for helix D. In solution, however, D55 apparently serves as a ligand to the bound Ca²⁺. When Mg²⁺ resides in site 2, the D55 carboxylate withdraws to a distance consistent with a role as an outer‐sphere ligand. ¹⁵N relaxation data, collected at 600 MHz, indicate that backbone mobility is limited in all three ligation states. Proteins 2013. © 2012 Wiley Periodicals, Inc.     

Synthesis,conformational study,and spectroscopic characterization of the cyclic Cα,α‐disubstituted glycine 9‐amino‐9‐fluorenecarboxylic acid

A series of terminally blocked peptides (to the pentamer level) from l ‐Ala and the cyclic C^α,α‐disubstituted Gly residue Afc and one Gly/Afc dipeptide have been synthesized by solution method and fully characterized. The molecular structure of the amino acid derivative Boc‐Afc‐OMe and the dipeptide Boc‐Afc‐Gly‐OMe were determined in the crystal state by X‐ray diffraction. In addition, the preferred conformation of all of the model peptides was assessed in deuterochloroform solution by FT‐IR absorption and ¹H‐NMR. The experimental data favour the conclusion that the Afc residue tends to adopt either the fully‐extended (C₅) or a folded/helical structure. In particular, the former conformation is highly populated in solution and is also that found in the crystal state in the two compounds investigated. A comparison with the structural propensities of the strictly related C^α,α‐disubstituted Gly residues Ac₅c and Dϕg is made and the implications for the use of the Afc residue in conformationally constrained analogues of bioactive peptides are briefly examined. A spectroscopic (UV absorption, fluorescence, CD) characterization of this novel aromatic C^α,α‐disubstituted Gly residue is also reported. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.     

The Skp1‐like protein SSK1 is required for cross‐pollen compatibility in S‐RNase‐based self‐incompatibility

The self‐incompatibility (SI) response occurs widely in flowering plants as a means of preventing self‐fertilization. In these self/non‐self discrimination systems, plant pistils reject self or genetically related pollen. In the Solanaceae, Plantaginaceae and Rosaceae, pistil‐secreted S‐RNases enter the pollen tube and function as cytotoxins to specifically arrest self‐pollen tube growth. Recent studies have revealed that the S‐locus F‐box (SLF) protein controls the pollen expression of SI in these families. However, the precise role of SLF remains largely unknown. Here we report that PhSSK1 (Petunia hybrida SLF‐interacting Skp1‐like1), an equivalent of AhSSK1 of Antirrhinum hispanicum, is expressed specifically in pollen and acts as an adaptor in an SCF(Skp1‐Cullin1‐F‐box)^SLF complex, indicating that this pollen‐specific SSK1‐SLF interaction occurs in both Petunia and Antirrhinum, two species from the Solanaceae and Plantaginaceae, respectively. Substantial reduction of PhSSK1 in pollen reduced cross‐pollen compatibility (CPC) in the S‐RNase‐based SI response, suggesting that the pollen S determinant contributes to inhibiting rather than protecting the S‐RNase activity, at least in solanaceous plants. Furthermore, our results provide an example that a specific Skp1‐like protein other than the known conserved ones can be recruited into a canonical SCF complex as an adaptor.     

Claisen–Schmidt condensation: Synthesis of (1S,6R)/(1R,6S)‐2‐oxo‐N,4,6‐triarylcyclohex‐3‐enecarboxamide derivatives with different substituents in H2O/EtOH

A simple, green, and direct three‐component condensation of acetophenone, aromatic aldehydes with 3‐oxo‐N‐phenylbutanamide (acetoacetanilide) to generate some novel (1S,6R)/(1R,6S)‐2‐oxo‐N,4,6‐triarylcyclohex‐3‐enecarboxamide derivatives was carried out over K₂CO₃ (10 mol%) with high efficiency in water/ethanol as green solvent at room temperature. This protocol proceeded via Claisen–Schmidt condensation and Michael addition. The present methodology offers several advantages, such as short reaction time, high yield, more readily available and inexpensive materials, more environmentally friendly, no need for column chromatography, simple work‐up procedure, and the absence of volatile and hazardous organic solvents.     

Effect of acidic pH on the stability of α‐synuclein dimers

Environmental factors, such as acidic pH, facilitate the assembly of α‐synuclein (α‐Syn) in aggregates, but the impact of pH on the very first step of α‐Syn aggregation remains elusive. Recently, we developed a single‐molecule approach that enabled us to measure directly the stability of α‐Syn dimers. Unlabeled α‐Syn monomers were immobilized on a substrate, and fluorophore‐labeled monomers were added to the solution to allow them to form dimers with immobilized α‐Syn monomers. The dimer lifetimes were measured directly from the fluorescence bursts on the time trajectories. Herein, we applied the single‐molecule tethered approach for probing of intermolecular interaction to characterize the effect of acidic pH on the lifetimes of α‐Syn dimers. The experiments were performed at pH 5 and 7 for wild‐type α?Syn and for two mutants containing familial type mutations E46K and A53T. We demonstrate that a decrease of pH resulted in more than threefold increase in the α‐Syn dimers lifetimes with some variability between the α‐Syn species. We hypothesize that the stabilization effect is explained by neutralization of residues 96–140 of α‐Syn and this electrostatic effect facilitates the association of the two monomers. Given that dimerization is the first step of α‐Syn aggregation, we posit that the electrostatic effect thereby contributes to accelerating α‐Syn aggregation at acidic pH. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 715–724, 2016.     

1‐Aminobenzocyclobutene‐1‐phosphonic Acid and Related Compounds as Inhibitors of Phenylalanine Ammonia‐Lyase

Five new geminal aminocycloalkanephosphonic acids ( 4 – 8 ) containing both an aromatic ring and a cycloalkane ring were synthesized and evaluated as potential inhibitors of buckwheat phenylalanine ammonia‐lyase (PAL). Within the set of compounds which are related to 2‐aminoindane‐2‐phosphonic acid (AIP, 3 ), a known powerful inhibitor of PAL, racemic 1‐aminobenzocyclobutene‐1‐phosphonic acid ( 4 ), was six times weaker than AIP as an in vitro inhibitor of buckwheat PAL, but six times stronger than AIP as an in vivo inhibitor of phenylalanine‐derived anthocyanin synthesis in buckwheat.