Microcalorimetric study of Escherichia coli growth inhibited by the selenomorpholine complexes

The inhibitory or antibiotic action of four kinds of the selenomorpholine complex on a strain of Escherichia coli was studied by microcalorimetry. Differences in their capacities to inhibit the metabolism of this bacterium were observed. The extent and duration of the inhibitory effect on the metabolism as judged from the rate constant, k, and the half-inhibitory concentration, IC₅₀, varied with the different drugs. The rate constant (k) of Escherichia coli (in the log phase) in the presence of the drugs decreased with increasing concentrations of the drugs (C). The relationship of k and C is nearly linear for (1) selenomorpholine and (2) selenomorpholine hydrochloride, but for (3) N,N′-methylene bisselenomorpholine and (4) N-dodecyl selenomorpholine, it is not linear. The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is (3) and (4)>(1)>(2).     

Cytotoxicity and enzymatic activity inhibition in cell lines treated with novel iminosugar derivatives

Iminosugars are monosaccharide analogues that have been demonstrated to be specific inhibitors for glycosidases and are currently used therapeutically in several human disorders. N-alkylated derivatives of d-fagomine and (2R,3S,4R,5S)-2-(hydroxymethyl)-5-methylpyrrolidine-3,4-diol with aliphatic chains were tested in eight human cancer cell lines to analyze their cytotoxicity and the inhibitory effect in the activities of specific glycosidases. Results indicate that these compounds were more cytotoxic as the length of the alkyl chain increases. N-dodecyl-d-fagomine inhibited specifically the α-d-glucosidase activity in cell lysates, whereas no effect was detected in other glycosidases. The N-dodecyl derivative of (2R,3S,4R,5S)-2-(Hydroxymethyl)-5-methylpyrrolidine-3,4-diol induced specific inhibition against α-l-fucosidase in cell lysates. Our results indicated that the length of the alkyl chain linked to the iminosugars determine their cytotoxicity as well as the inhibitory effect on the enzymatic activities of specific glycosidases, in human cancer cell lines.     

常绿阔叶林8种乔灌木叶片氮含量及其分配与光合能力的关系

以浙江天童国家森林公园常绿阔叶林为研究对象,采用空间代替时间的方法,研究了5个不同演替阶段常见的4种乔木以及4种灌木叶片的光饱和速率(Pmax)、光合氮素利用效率(PNUE)及其与叶片氮含量(NL)、叶片氮素在细胞壁的分配比例(细胞壁N/叶片总N,NCW/NL)、氮素在光合酶中的分配比例(NR/NL)、单位面积叶干重(LMA)的相互关系。结果表明:(1)演替系列4种乔木和4种灌木各种间指标除NL外均表现出显著差异,前期种较后期种具有更高的NR/NL、PNUE、Pmax,而后期种LMA、NCW/NL、MCW/ML(细胞壁干重/叶片总干重)更大,NL在乔木各种间差异不明显,在灌木种间则差异显著;乔木种较灌木种具有更大的LMA、NCW/NL、MCW/ML,而NR/NL则较灌木小;8种植物的Pmax与NL以杨梅为最高,连蕊茶最低;苦槠具有最高的PNUE,而栲树最低。(2)随着演替的进行,前期种的NR/NL、PNUE、Pmax有减小趋势,而LMA、NCW/NL、MCW/ML逐渐增大,后期种则表现出相反的趋势。(3)NR/NL与Pmax、PNUE之间呈显著正相关关系,而LMA、NCW/NL、MCW/ML则与Pmax、PNUE、NR/NL显著负相关。研究认为,NR/NL与NCW/NL之间的负相关性及其对PNUE的影响可以在一定程度上解释树木在光合与维持两方面的权衡关系以及演替的生理机制。     

The Importance of Molecular Parameters of Quaternary Ammonium Salts in Their Antigibberellin (Retardant) Activity

The importance of six theoretically calculated molecular parameters in the antigibberellin (retardant) activity of quaternary ammonium salts is studied using a regression analysis. A bioassay system based on cell culture of fungus Gibberella fujikuroi is used to determine the activity. In the case of N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium chloride (choline) and N,N,N-triethyl-N-(2-hydroxyethyl)ammonium chloride (N,N,N-triethylcholine) derivatives with linear structure, the polarizability, proton acceptor activity, and lipophilicity of these compounds exert the largest effect on the antigibberellin activity. The antigibberellin activity of more sterically hindered N,N-dialkylpiperidinium salts was mainly defined by the steric parameter, while the polarizability, proton acceptor activity, and (through them) lipophilicity exert a lesser effect. Other parameters are of minor importance for the three groups of compounds studied.     

Inhibitory Effects of Cysteine and Cysteine Derivatives on Germination of Sporangiospores and Hyphal Growth of Different Zygomycetes

The in vitro antifungal activity of cysteine (d- and l-cysteine) and its four derivatives (l-cysteine-methyl-ester, N-acetyl-cysteine, N-isobutyryl-d-cysteine, and N-isobutyryl-l-cysteine) were investigated on 20 fungal isolates representing 16 genera (Absidia, Actinomucor, Backusella, Gilbertella, Micromucor, Mortierella, Mucor, Mycotypha, Phycomyces, Rhizomucor, Rhizopus, Saksenaea, Syncephalastrum, Thamnostylum, Umbellopsis, and Zygorynchus). The inhibitory potential of different concentrations of these compounds, ranging from 0.625 to 10 mM, were investigated on the germination of sporangiospores as well as on hyphal extension, using broth microdilution method and agar plate test. Treatment with cysteine and its derivatives resulted in a strong inhibition in most studied strains. At 10 mM of compounds, complete blockage of growth was observed for some isolates. Sensitive species exhibited severe changes in colony morphology in the presence of 10 mM l-cysteine, N-acetyl-cysteine, and N-isobutyryl-l-cysteine. Microscopic observations revealed that 10 mM N-acetyl-cysteine induced dramatic modifications in the structural organization of the hyphae. Results suggest that cysteine and its derivatives have a therapeutic potential against fungal infections caused by Zygomycetes species.     

Optical anisotropies of amides and peptides in dioxane

The molar Kerr constants _mK, molar refractions _mR, and dipole moments μ are reported for the N-methylacetamides CX₃CONHCH₃ (X = H, CH₃, F. CI, Br) and acetamides CX₃CONH₂ (X = H, F, Cl, Br). The components of the polarizability tensor α are deduced for N-methylacetamide and acetamide on the basis of the bond additivity approximation. This α is found to be considerably more anisotropic than was indicated in previous determinations by other methods. The data for N-methylacetamide were used to calculate _mK, μ, and γ² (anisotropy squared) of N-acetyl-N′-methylglycine amide and N-acetyl-N′-methyl-alanine amide as functions of the torsional angles (?,Ψ). The statistical mechanical averages of _mK, μ, and γ² were calculated from conformational energies obtained by the methods of Scheraga.     

Synthesis, characterization, and antibacterial activity of N,O-quaternary ammonium chitosan

N,N,N-Trimethyl O-(2-hydroxy-3-trimethylammonium propyl) chitosans (TMHTMAPC) with different degrees of O-substitution were synthesized by reacting O-methyl-free N,N,N-trimethyl chitosan (TMC) with 3-chloro-2-hydroxy-propyl trimethyl ammonium chloride (CHPTMAC). The products were characterized by ¹H NMR, FTIR and TGA, and investigated for antibacterial activity against Staphylococcus aureus and Escherichia coli under weakly acidic (pH 5.5) and weakly basic (pH 7.2) conditions. TMHTMAPC exhibited enhanced antibacterial activity compared with TMC, and the activity of TMHTMAPC increased with an increase in the degree of substitution. Divalent cations (Ba²⁺ and Ca²⁺) strongly reduced the antibacterial activity of chitosan, O-carboxymethyl chitosan and N,N,N-trimethyl-O-carboxymethyl chitosan, but the repression on the antibacterial activity of TMC and TMHTMAPC was weaker. This indicates that the free amino group on chitosan backbone is the main functional group interacting with divalent cations. The existence of 100 mM Na⁺ slightly reduced the antibacterial activity of both chitosan and its derivatives.     

<Emphasis Type="Italic">N</Emphasis>-glycan moieties of the crustacean egg yolk protein and their glycosylation sites

Vitellogenin (Vg) is the precursor of the egg yolk glycoprotein of crustaceans. In the prawn Macrobrachium rosenbergii, Vg is synthesized in the hepatopancreas, secreted to the hemolymph, and taken up by means of receptor-mediated endocytosis into the oocytes. The importance of glycosylation of Vg lies in its putative role in the folding, processing and transport of this protein to the egg yolk and in the fact that the N-glycan moieties could provide a source of carbohydrate during embryogenesis. The present study describes, for the first time, the structure of the glycan moieties and their sites of attachment to the Vg of M. rosenbergii. Bioinformatics analysis revealed seven putative N-glycosylation sites in M. rosenbergii Vg; two of these glycosylation sites are conserved throughout the Vgs of decapod crustaceans from the Pleocyemata suborder (N ¹⁵⁹ and N ⁶⁶⁰). The glycosylation of six putative sites of M. rosenbergii Vg (N ¹⁵¹, N ¹⁵⁹, N _,¹⁶⁸ N _,⁶¹⁴ N ⁶⁶⁰ and N ²³⁰⁰) was confirmed; three of the confirmed glycosylation sites are localized around the N-terminally conserved N-glycosylation site N ¹⁵⁹. From a theoretical three-dimensional structure, these three N-glycosylated sites N ¹⁵¹, N ¹⁵⁹, and N ¹⁶⁸ were localized on the surface of the Vg consensus sequence. In addition, an uncommon high mannose N-linked oligosaccharide structure with a glucose cap (Glc₁Man₉GlcNAc₂) was characterized in the secreted Vg. These findings thus make a significant contribution to the structural elucidating of the crustacean Vg glycan moieties, which may shed light on their role in protein folding and transport and in recognition between Vg and its target organ, the oocyte.     

Effects of composition and polymerization conditions on crosslinked polymer supports based on N-acrylyl pyrrolidine and N,N-dimethyl acrylamide for peptide synthesis

Poly(N-acrylyl pyrrolidine-co-N,N′-bis(acrylyl) 1,2-diaminoethane-co-N-Acrylyl 1,6-diamino hexane HCl) with 2,5,8,11,12,15, and 20% degrees of crosslinking (DC) and poly-(N,N′-dimethylacrylaminde-co-N,N′-bis(acrylyl) 1,2-diaminoethane-co-N-acrylyl 1,6-diamino hexane HCl) with 2,5,10, and 15% DC have been synthesized in an entirely beaded form by reverse-phase suspension polymerization. The monomer-to-water ratio was kept constant for all these polymers. With the exception of 2% crosslinked resins in the PAP and PDMA groups, all the resins exhibited favorable swelling properties in solvents normally used for peptide synthesis and the percent incorporation of the first amino acid residue was close to 100 for DC of up to 20%. This is explained as due to the flexible and polar characteristics of the crosslinking agent, N,N′-bis(acrylyl) 1,2-diaminoethane. Between 5 and 20% DC the degree of swelling of the resins changes only slightly with increasing DC. This effect of DC on the swelling and percent incorporation of the first amino acid residue is more favorable for peptide synthesis than in the case of divinyl benzene crosslinked poly(styrene).     

Synthesis of new N-substituted 3,4,5-trihydroxypiperidin-2-ones from d-ribono-1,4-lactone

d-Ribono-1,4-lactone was treated with ethylamine in DMF to afford N-ethyl-d-ribonamide 8a in quantitative yield. Using this reaction procedure, N-butyl, N-hexyl, N-dodecyl, N-benzyl, N-(3-methyl-pyridinyl)-, N-(2-hydroxy-ethyl)-, and N-(2-cyano-ethyl)-d-ribonamides 8b-h were obtained in quantitative yield. Bromination of the amides 8a-e with acetyl bromide in dioxane followed by acetylation gave 2,3,4-tri-O-acetyl-5-bromo-5-deoxy-N-ethyl, N-butyl, N-hexyl, N-dodecyl, and N-benzyl-d-ribonamides 9a-e in 40-54% yields. To obtain 2,3,4-tri-O-acetyl-5-bromo-5-deoxy-N-(3-methyl-pyridinyl)-, N-(2-hydroxy-ethyl)-, and N-(2-cyano-ethyl)-9f-h, the bromination is necessary before the amidation reaction. Treatment of the bromoamides 9a-h with NaH in DMF followed by methanolysis affords N-alkyl-d-ribono-1,5-lactams 12a-h in quantitative yield.     

Synthesis and properties of chitosan hydrogels modified with heterocycles

Preparation and properties of chitosan modified with heterocycles in absence or presence of gluteraldehyde as a cross linker is described. New modified chitosan–heterocyclic hydrogels were prepared from chitosan and heterocyclic compounds such as N,N′-biisomaleimide, N,N′-biisophthalimide, and N,N′-phthalimidomaleimide via a crosslinking reaction. The new hydrogels chemical structure was characterized by spectral analysis (IR), X-ray diffraction, thermal gravimetric analysis (TGA), solubility, and swellability in water and different organic solvents. Evaluation of the efficiency of the new hydrogels to uptake copper and cobalt ions from aqueous systems was carried out and promising results were obtained.     

Inhibition of the biosynthesis ofN-acetylneuraminic acid by metal ions and seleniumin vitro

In liver homogenate the biosynthesis ofN-acetylneuraminic acid usingN-acetylglucosamine as precursor can be followed stepwise by applying different chromatographic procedures. In this cell-free system 16 metal ions (Zn²⁺, Mn²⁺, La³⁺, Co²⁺, Cu²⁺, Hg²⁺, VO ₃ ^– , Pb²⁺, Ce³⁺, Cd²⁺, Fe²⁺, Fe³⁺, Al³⁺, Sn²⁺, Cs⁺ and Li⁺) and the selenium compounds, selenium(IV) oxide and sodium selenite, have been checked with respect to their ability to influence a single or possible several steps of the biosynthesis ofN-acetylneuraminic acid. It could be shown that the following enzymes are sensitive to these metal ions (usually applied at a concentration of 1 mmoll^–1):N-acetylglucosamine kinase (inhibited by Zn²⁺ and vandate), UDP-N-acetylglucosamine-2-epimerase (inhibited by zn²⁺, Co²⁺, Cu²⁺, Hg²⁺, VO ₃ ^– , Pb²⁺, Cd²⁺, Fe³⁺, Cs⁺, Li⁺, selenium(IV) oxide and selenite), andN-acetylmannosamine kinase (inhibited by Zn²⁺, Cu²⁺, Cd²⁺, and Co²⁺). Dose dependent measurements have shown that Zn²⁺, Cu²⁺ and selenite are more efficient inhibitors of UDP-N-acetylglucosamine-2-epimerase than vanadate. As for theN-acetylmannosamine kinase inhibition, a decreasing inhibitory effect exists in the following order Zn²⁺, Cd²⁺, Co²⁺ and Cu²⁺. In contrast, La³⁺, Al³⁺ and Mn²⁺ (1 mmoll^–1) did not interfere with the biosynthesis ofN-acetylneuraminic acid. Thus, the conclusion that the inhibitory effect of the metal ions investigated cannot be regarded as simply unspecific is justified.Dedicated to Professor Theodor Günther on the occasion of his 60th birthday     

帽儿山地区不同土地利用方式下土壤-微生物-矿化碳氮化学计量特征

土地利用方式的变化导致土壤碳氮含量及其化学计量关系的变化,然而土壤微生物化学计量及其驱动的碳氮矿化过程如何响应这种变化仍不明确。以帽儿山地区天然落叶阔叶林、人工红松林、草地和农田4种不同土地利用类型为对象,测定其土壤有机碳(C_(soil))、全氮(N_(soil))、微生物生物量碳和氮(C_(mic)和N_(mic))、土壤碳和氮矿化速率(C_(min)和N_(min)),旨在比较不同土地利用方式对土壤、微生物碳氮化学计量特征及矿化速率的影响,探索土壤-微生物-矿化之间碳氮化学计量特征的相关性,揭示微生物对土壤碳氮化学计量变化的响应和调控机制。结果显示:C_(soil)、N_(soil)、C_(mic)、N_(mic)和C_(min)均呈现天然落叶阔叶林人工红松林草地农田,而天然落叶阔叶林和草地的N_(min)显著高于人工红松林和农田。土地利用方式显著影响土壤和微生物碳氮比(C∶N_(soil)和C∶N_(mic)),均呈现农田最高。不同土地利用方式的数据综合分析发现:碳氮矿化速率比与C∶N_(mic)呈负相关,而和微生物与土壤碳氮化学计量不平衡性(C∶N_(imb))显著正相关。单位微生物生物量的碳矿化速率(qCO_2)随着C∶N_(mic)的增加而降低,而单位微生物生物量的氮矿化速率(qAN)随着C∶N_(mic)的增加而增加。C∶N_(imb)与qCO_2正相关,与qAN负相关。以上结果表明,微生物会通过改变自身碳氮化学计量、调整碳氮之间相对矿化速率,以适应土地利用变化导致的土壤碳氮及其化学计量的变异性,以满足自身生长和代谢的碳氮需求平衡。     

Interactions between enhancer of rudimentary and Notch and deltex reveal a regulatory function of enhancer of rudimentary in the Notch signaling pathway in Drosophila melanogaster

Enhancer of rudimentary, e(r), encodes a small nuclear protein, ER, that has been implicated in the regulation of pyrimidine metabolism, DNA replication, and cell proliferation. In Drosophila melanogaster, a new recessive Notch allele, N^nd-p, was isolated as a lethal in combination with an e(r) allele, e(r)^p2. Both mutants are viable as single mutants. N^nd-p is caused by a P-element insertion in the 5' UTR, 378-bp upstream of the start of translation. Together the molecular and genetic data argue that N^nd-p is a hypomorphic allele of N. The three viable notchoid alleles, N^nd-p, N^nd-1, and N^nd-3, are lethal in combination with e(r)^- alleles. Our present hypothesis is that e(r) is a positive regulator of the Notch signaling pathway and that the lethality of the Ne(r) double mutants is caused by a reduction in the expression of the pathway. This is supported by the rescue of the lethality by a mutation in Hairless, a negative regulator of N, and by the synthetic lethality of dxe(r) double mutants. Further support for the hypothesis is a reduction in E(spl) expression in an e(r)^- mutant. Immunostaining localizes ER to the nucleus, suggesting a nuclear function for ER. A role in the Notch signaling pathway, suggests that e(r) may be expressed in the nervous system. This turns out to be the case, as immunostaining of ER shows that ER is localized to the developing CNS.     

Interactions of a few azole derivatives with a transport protein: role of heteroatoms

The interaction of a few azole derivatives, 2‐(4′‐N,N‐dimethylaminophenyl)benzimidazole, 2‐(4′‐N,N‐dimethylaminophenyl)benzoxazole, 2‐(4′‐N,N‐dimethylaminophenyl)oxazolo[4,5‐b]pyridine with bovine serum albumin (BSA) were examined by absorption and fluorescence spectroscopy. The results were compared with the previously studied imidazopyridine derivative 2‐(4′‐N,N‐dimethylaminophenyl)imidazo[4,5‐b]pyridine. Displacement studies were carried out with site selective probes to locate the binding site of these ligands. The spectral shifts and the binding constant vary depending on the nature of the ligand. The fluorescence intensity of both oxazole derivatives 2‐(4′‐N,N‐dimethylaminophenyl)benzoxazole and 2‐(4′‐N,N‐dimethylaminophenyl) oxazolo[4,5‐b]pyridine increases substantially in the presence of BSA, whereas the intensity of 2‐(4′‐N,N‐dimethylaminophenyl)benzimidazole decreases. However, hypsochromic shift is observed in presence of BSA. The results obtained from the docking studies are also in good agreement with the experimental results. The location and orientation of binding depend upon the nature of the ligand. The studies revealed that apart from hydrophobic interaction, hydrogen bonding also plays a vital role in the molecular binding. Oxazoles have higher binding affinity than imidazoles and substitution of extra nitrogen further increases the binding affinity. Copyright © 2015 John Wiley & Sons, Ltd.     

Characterization of Foam- and Emulsion-stabilizing Functions of Enzymatically Modified Proteins with Surfactancy

A papain-catalyzed reaction involving covalent incorporation of l-leucine n-alkyl ester is available for producing an enzymatically modified protein (EMP) with surfactancy [Agric. Biol. Chem., 45, 1621 (1981)]. In the present work we used gelatin as a starting material and incorporated l-leucine n-hexyl ester to produce a whippable EMP and l-leucine n-dodecyl ester to produce an emulsifiable EMP. A foam system formed with the whippable EMP was much stabler than that formed with sodium dodecylsulfate. The emulsifiable EMP also gave a much stabler oil-in-water emulsion than Tween-80 did. The stability of the emulsion formed with EMP was not affected by the presence of NaCl at a very high concentration. The observed foam and emulsion stabilities were well explained by the data for decreased mobility of the involved water protons. These results may indicate that EMP molecules, when arranged at the air/water or oil/water interface, can bind a part of the water to form thick barriers which prevent the air or oil particles from coalescing.     

Isobutyl Amides from Pepper (Piper nigrum L.)

Four isobutyl amides were isolated from the fruits of white pepper (Piper nigrum L.) and identified to be N-isobutyl-13-(3,4-methylenedioxyphenyl)-2E,4E,12E-tridecatrienamide (3, guineensine), N-isobutyl-2E,4E,8Z-eicosatrienamide (5), N-isobutyl-2E,4E-octadecadienamide (6) and N-isobutyl-2E,4E-decadienamide (7, pellitorine).     

Isolation of Ceramides from Tagetes patula L. Yellow Flowers and Nematicidal Activity of the Fractions and Pure Compounds against Cyst Nematode,Heterodera zeae

Investigation of yellow flower extract of Tagetes patula L. led to the identification of an aggregate of five phytoceramides. Among them, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]icosanamide, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]heneicosanamide, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]docosanamide, and (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]tricosanamide were identified as new compounds and termed as tagetceramides, whereas (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]tetracosanamide was a known ceramide. A steroid (β‐sitosterol glucoside) was also isolated from the subsequent fraction. The structures of these compounds were determined on the basis of spectroscopic analyses, as well as chemical method. Several other compounds were also identified by GC/MS analysis. The fractions and some commercial products, a ceramide HFA, β‐sitosterol, and stigmasterol were evaluated against an economically important cyst nematode, Heterodera zeae. Ceramide HFA showed 100 % mortality, whereas, β‐sitosterol and stigmasterol were 40–50 % active, at 1 % concentration after 24 h of exposure time, while β‐sitosterol glucoside revealed no activity against the nematode.     

Increased plasticity of genomic imprinting of Dlk1 in brain is due to genetic and epigenetic factors

The expression of six imprinted genes (Dlk1, Gtl2, Igf2r, Kcnq1, Nnat, and Peg1) was examined in brains of 21 mice derived from N₂ × N₂ intercrosses between C57BL/6 and MOLF/Ei strains. Imprinting of Igf2r, Kcnq1, Gtl2, and Dlk1 varied among individuals. As three of these genes are implicated in cell–cell signaling or cell–environment interactions, variation in their imprinting may influence a wide range of biological processes from cell differentiation to behavior. To elucidate the mechanisms underlying the interindividual imprinting variation in the brain, we focused our effort on the paternally expressed gene Dlk1. We investigated expression of Dlk1 in the brains of animals from N₉ and N₁₀ backcrosses and found that reactivation of the normally silent maternal Dlk1 allele in the N₉ and N₁₀ mice occurred less often than in N₂ × N₂ animals. Our data suggest that trans-acting genetic factors of MOLF/Ei origin facilitate the reactivation of the normally silent maternal allele of Dlk1. We mapped one of these factors to the proximal part of Chr 7. The results of bisulfite sequencing methylation analysis show that reactivation of the maternal allele was also associated with hypermethylation of the intragenic differentially methylated region (IG DMR), which is the imprinting control region for the Dlk1–Gtl2 domain. Thus, the imprinting status of Dlk1 in the brain depends upon trans-acting genetic influences and correlates with the methylation status of a specific subregion of the IG DMR.The GenBank accession numbers for sequences described in this article are AY644388–644394.     

Axial chirality in biaryl N,N-dialkylaminopyridine derivatives bearing an internal carboxy group

Axial chirality in N,N-dimethylaminopyridines as well as N,N-dipropylaminopyridines bearing an internal carboxy group were evaluated based on their racemization barriers and circular dichroism spectra. The half-life of racemization of N,N-dipropylaminopyridine derivative 2 was estimated to be 19.7 days at 20°C. Its enantiomers isolated as optically active forms showed positive-negative and negative-positive Cotton effects for (+)- 2 and (−)- 2 , respectively, from 310 to 210 nm. Furthermore, (−)- 2 was applied as a chiral nucleophilic catalyst and exhibited asymmetric induction in acylative kinetic resolution of 1-(1-naphthyl)ethane-1-ol.