叔丁氧羰基-叔亮氨酸(Boc-tert-leucine)的合成研究

对叔亮氨酸的氨基的叔丁氧羰基(Boc)保护反应条件进行了研究,最佳反应条件是:以四氢呋喃-水为反应溶剂体系,两者体积比为1:1,叔亮氨酸反应浓度为25 mg.mL-1,最佳收率可达90.63﹪。

Acetyl-DL-leucine对猫单侧前庭神经切断后运动平衡能力和前庭外侧核神经元放电活动恢复的影响

本文观测了Ａｃｅｔｙｌ－ＤＬ－ｌｅｕｃｉｎｅ（ＡＬ、一种抗眩晕药）对猫单侧前庭神经切断后前庭代偿的影响。结果显示：ＡＬ加快术后猫在转动横梁测试中运动平衡能力的恢复，但抑制去传入前庭外侧核神经元（ｎ＝５０６）静息自发放电频率的恢复。ＡＬ促进放电活动与头部左右摆动体位相关的神经元数量和比例的恢复，从术后的第１周的１０％（ｎ＝４５４），逐渐提高到术后第３周的６０％，第５周的７５％

Differential regulation of protein synthesis in skeletal muscle and liver of neonatal pigs by leucine through an mTORC1-dependent pathway

Neonatal growth is characterized by a high protein synthesis rate that is largely due to an enhanced sensitivity to the postprandial rise in insulin and amino acids, especially leucine. The mechanism of leucine＇s action in vivo is not well understood. In this study, we investigated the effect of leucine infusion on protein synthesis in skeletal muscle and liver of neonatal pigs. To evaluate the mode of action of leucine, we used rapamycin, an inhibitor of mammalian target of rapamycin （mTOR） complex-1 （mTORC1）. Overnight-fasted 7-day-old piglets were treated with rapamycin for 1 hour and then infused with leucine （400 μmol·kg^-1·h^-1） for 1 hour. Leucine infusion increased the rate of protein synthesis, and ribosomal protein S6 kinase 1 （S6K1） and eukaryotic initiation factor （elF） 4E-binding protein-1 （4E-BP1） phosphorylation in gastrocnemius and masseter muscles （P 〈 0.05）, but not in the liver. The leucine-induced stimulation of protein synthesis and S6K1 and 4E-BP1 phosphorylation were completely blocked by rapamycin, suggesting that leucine action is by an mTORC1-dependent mechanism. Neither leucine nor rapamycin had any effect on the activation of the upstream mTQRC1 regulators, AMP-activated protein kinase and protein kinase B, in skeletal muscle or liver. The activation of elF2α and elongation factor 2 was not affected by leucine or rapamycin, indicating that these two pathways are not limiting steps of leucine-induced protein synthesis. These results suggest that leucine stimulates muscle protein synthesis in neonatal pigs by inducing the activation of mTORC1 and its downstream pathway leading to mRNA translation.

Genome-wide analysis of basic leucine zipper transcription factor families in Arabidopsis thaliana,Oryza sativa and Populus trichocarpa

The basic leucine zipper （bZIP） transcription factors form a large gene family that is important in pathogen defense, light and stress signaling, etc. The Completed whole genome sequences of model plants Arabidopsis （Arabidopsis thaliana）, rice （Oryza sativa） and poplar （Populus trichocarpa） constitute a valuable resource for genome-wide analysis and genomic comparative analysis, as they are representatives of the two major evolutionary lineages within the angiosperms： the monocotyledons and the dicotyledons. In this study, bioinformatics analysis identified 74, 89 and 88 bZIP genes respectively in Arabidopsis, rice and poplar. Moreover, a comprehensive overview of this gene family is presented, including the gene structure, phylogeny, chromosome distribution, conserved motifs. As a result, the plant bZIPs were organized into 10 subfamilies on basis of phylogenetic relationship. Gene duplication events during the family evolution history were also investigated. And it was further concluded that chromosomal/segmental duplication might have played a key role in gene expansion of bZIP gene family.

Leucine signaling in the pathogenesis of type 2 diabetes and obesity

Epidemiological evidence points to increased dairy and meat consumption,staples of the Western diet,as major risk factors for the development of type 2 diabetes(T2D).This paper presents a new concept and comprehensive review of leucine-mediated cell signaling explaining the pathogenesis of T2D and obesity by leucine-induced over-stimulation of mammalian target of rapamycin complex 1(mTORC1).mTORC1,a pivotal nutrient-sensitive kinase,promotes growth and cell proliferation in response to glucose,energy,growth factors and amino acids.Dairy proteins and meat stimulate insulin/insulin-like growth factor 1 signaling and provide high amounts of leucine,a primary and independent stimulator for mTORC1 activation.The downstream target of mTORC1,the kinase S6K1,induces insulin resistance by phosphorylation of insulin receptor substrate-1,thereby increasing the metabolic burden of β-cells.Moreover,leucine-mediated mTORC1-S6K1-signaling plays an important role in adipogenesis,thus increasing the risk of obesity-mediated insulin resistance. High consumption of leucine-rich proteins explains exaggerated mTORC1-dependent insulin secretion, increased β-cell growth and β-cell proliferation promoting an early onset of replicative β-cell senescence with subsequent β-cell apoptosis.Disturbances of β-cell mass regulation with increased β-cell proliferation and apoptosis as well as insulin resistance are hallmarks of T2D,which are all associated with hyperactivation of mTORC1.In contrast,the anti-diabetic drug metformin antagonizes leucine-mediated mTORC1 signaling.Plant-derived polyphenols and flavonoids are identified as natural inhibitors of mTORC1 and exert anti-diabetic and anti-obesity effects.Furthermore,bariatric surgery in obesity reduces increased plasma levels of leucine and other branched-chain amino acids.Attenuation of leucine-mediated mTORC1 signaling by defining appropriate upper limits of the daily intake of leucine-rich animal and dairy proteins may offer a great chance for the prevention of T2D and obesity,as well as other epidemic diseases of civilization with increased mTORC1 signaling,especially cancer and neurodegenerative diseases,which are frequently associated with T2D.

Dietary Leucine Requirement for Juvenile Large Yellow Croaker Pseudosciaena crocea (Richardson,1846)

Dietary leucine requirement for juvenile large yellow croaker, Pseudosciaena crocea Richardson 1846 (initial body weight 6.0 g±0.1 g) was determined using dose-response method.Six isonitogenous (crude protein 43%) and isoenergetic (19 kJ g-1) practical diets containing six levels of leucine (Diets 1-6) ranging from 1.23% to 4.80% (dry matter) were made at about 0.7% increment of leucine.Equal amino acid nitrogen was maintained by replacing leucine with glutamic acid.Triplicate groups of 60 individuals were fed to apparent satiation by hand twice daily (05:00 and 17:30).The water temperature was 26-32℃, salinity 26-30 and dissolved oxygen approximately 7 mg L-1 during the experimental period.Final weight (FW) of large yellow croaker initially increased with increasing level of dietary leucine but then decreased at further higher level of leucine.The highest FW was obtained in fish fed diet with 3.30% Leucine (Diet 4).FW of fish fed the diet with 4.80% Leucine (Diet 6) was significantly lower than those fed Diet 4.However, no significant differences were observed between the other dietary treatments.Feed efficiency (FE) and whole body composition were independent of dietary leucine contents (P>0.05).The results indicated that leucine was essential for growth of juvenile large yellow croaker.On the basis of FW, the optimum dietary leucine requirement for juvenile large yellow croaker was estimated to be 2.92% of dry matter (6.79% of dietary protein).

Dietary Leucine Requirement of Juvenile Japanese Seabass(Lateolabrax Japonicus)

A 56-day feeding trial was conducted to examine the dietary leucine requirement of juvenile Japanese seabass in sea- water floating net cages （1.5 m × 1.5 m × 2.0 m）. Six isonitrogenous （crude protein 40%） and isoenergetic （gross energy 20 kJ g-1） diets were formulated to contain different concentrations of leucine （0.9%, 1.49%, 2.07%, 2.70%, 3.30% and 3.88% of dry matter）. Crys- talline L-amino acids were supplemented to simulate the whole body amino acid pattern of Japanese seabass except for leucine. Three groups （30 fish individuals each, 8.0g±0.20g in initial weight） were fed to apparent satiation at 5：00 and 17：30 every day. During the experimental period, the water temperature ranged from 26 to 32℃ and salinity from 26 to 30, and the dissolved oxygen was maintained at 7mgL-l. The results showed that weight gain （WG）, nitrogen retention （NR）, feed efficiency （FE） and protein efficiency ratio （PER） were significantly increased when dietary leucine was increased from 0.90% to 2.70% of dry matter, and then declined. WG was the highest when fish were fed D4 containing 2.70% of leucine. No significant differences were observed in body composition among dietary treatments （P 〉 0.05）. Considering the change of WG, the optimum dietary leucine requirement of juve- nile Japanese seabass was either 2.39% of dry matter or 5.68% of dietary protein.

Leucine Supplementation in a Chronically Protein-Restricted Diet Enhances Muscle Weight and Postprandial Protein Synthesis of Skeletal Muscle by Promoting the mTOR Pathway in Adult Rats

Low protein intake causes a decrease in protein deposition in most animal tissues. The purpose of this study was to investigate whether leucine supplementation would increase the synthesis rate of protein and muscle weight in adult rats, which chronically consume only 58.8% of their protein requirements. Thirty-six male Sprague-Dawley rats were assigned to one of three dietary treatments including a 20% casein diet （CON）, a 10% casein ＋ 0.44% alanine diet （R）, and a 10% casein ＋ 0.87% leucine diet （RL）. After a 10 d dietary treatment, plasma amino acid levels were measured after feeding, the gastrocnemius muscles and soleus muscles were harvested and weighed, and the fractional synthesis rate （FSR） and mammalian target of rapamycin （mTOR） signaling proteins in skeletal muscle were measured. Regarding the plasma amino acid level, the RL group had the highest concentration of leucine （P 〈 0.05） and the lowest concentration of isoleucine （P 〈 0.05） among the three groups, and the CON group had a lower concentration of valine （P 〈 0.05） than the R and RL groups. Compared with the R and RE groups, the CON group diet significantly increased （P 〈 0.05） feed intake, protein synthesis rate, and the phosphorylation of eukaryutic initiation factor 4E binding protein 1 （4E-BP1）, and decreased the weight of abdominal adipose. Compared with the R group, the RL group significantly increased in gastrocnemius muscle weight, protein synthesis rate, and phosphorylation of both ribosomal protein $6 kinase 1 （56K1） and 4E-BP1. In conclusion, when protein is chronically restricted in adult rat diets, leucine supplementation moderately improves body weight gain and increases muscle protein synthesis through mTOR activation,

Application of quartz crystal nanobalance in conjunction with a net analyte signal based method for simultaneous determination of leucine, isoleucine and valine

The aim of the present investigation was to develop a biosensor for the detection of amino acids, Leucine, Isoleucine and Valine based on a quartz crystal nanobalance. leucine (Leu), isoleucine (Ile), and valine (Val) were selectively determined by quartz crystal nanobalance (QCN) sensor in conjunction with net analyte signal (NAS)-based method called HLA/GO. An orthogonal design was applied for the formation of calibration and prediction sets including Leu, Ile and Val compounds. The selection of the optimal time range involved the calculation of the net analyte sig-nal regression plot in any considered time window for each test sample. The searching of a region with maximum linearity of NAS regression plot (minimum error indicator) and minimum of PRESS value was carried out by applying a moving window strategy. On the base of obtained results, the differences on the adsorption profiles in the time range between 1 and 300 s were used to determine mixtures of compounds by HLA/GO method. The results showed that the method was successfully applied for the determina-tion of Leu, Ile and Val.

Effects of “Bioactive” amino acids leucine, glutamate, arginine and tryptophan on feed intake and mRNA expression of relative neuropeptides in broiler chicks

Feed intake control is vital to ensuring optimal nutrition and achieving full potential for growth and development in poultry. The aim of the present study was to investigate the effects of L-leucine, L-glutamate, L-tryptophan and L-arginine on feed intake and the mRNA expression levels of hypothalamic Neuropeptide involved in feed intake regulation in broiler chicks. Leucine, glutamate, tryptophan or arginine was intra-cerebroventricularly （ICV） administrated to 4d-old broiler chicks respectively and the feed intake were recorded at various time points. Quantitative PCR was performed to determine the hypothalamic mRNA expression levels of Neuropeptide Y （NPY）, agouti related protein （AgRP）, pro-opiomelanocortin （POMC）, melanocortin receptor 4 （MC4R） and corticotrophin releasing factor （CRF）. Our results showed that ICV administration of L-leucine （0.15 or 1.5 μmol） significantly （P〈0.05） increased feed intake up to 2 h post-administration period and elevated both hypothalamic NPY and AgRP mRNA expression levels. In contrast, ICV administration of L-glutamate （1.6 μmol） significantly （P 〈 0.05） decreased feed intake 0.25, 0.5 and 2 h post-injection, and increased hypothalamic CRF and MC4R mRNA expression levels. Meanwhile, both L-tryptophan （10 or 100 μg） and L-arginine （20 or 200 μg） had no significant effect on feed intake. These findings suggested that L-leucine and L-glutamate could act within the hypothalamus to influence food intake, and that both orexigenic and anorexigenic Neuropeptide genes might contribute directly to these effects.

Variability in the empirical leucine-to-carbon conversion factors along an environmental gradient

Bacterial production is one of the key parameters to evaluate bacterial role in ocean carbon fluxes.Estimation of bacterial production requires the leucine-to-carbon conversion factors that change widely across environments.However,empirical leucine-to-carbon conversion factors（e CFs） are seldom determined in situ because of time consuming and little is known on regulating factors for the e CFs.During May 2015 to January 2016,fourteen dilution experiments were conducted,from the Zhujiang（Pearl River） Estuary to the coast of the northern South China Sea,to determine spatiotemporal variability in the e CFs and its potential controlling factors along an environmental gradient.The e CFs showed clear spatial variations with the highest（1.27–1.69（kg C）/（mol Leu）） in low salinity waters（salinity〈15）,intermediate（1.03–1.25（kg C）/（mol Leu）） in moderate salinity（salinity of 15–25）,and the lowest（0.48–0.85（kg C）/（mol Leu）） in high salinity waters（salinity〉25）.Substrate availability was responsible for spatial variability in the e CFs.In the pristine coastal waters,low e CFs was related to substrate limitation and leucine incorporated was respired to maximize the survival rather than bacterial production.Hence,the e CFs measurement was needed for estimating bacterial production accurately in various marine environments.

Effects of Valine and Leucine on Some Antioxidant Enzymes in Hypercholesterolemic Rats

Objective: Reactive oxygen species (ROS) are involved in the endothelial-mediated disorders within atherosclerosis. Considering that an oxidant/antioxidant imbalance might be a key factor in the damaging ROS-mediated effects, the present study intends to determine the influence of a high-fat diet, associated with essential amino acids—valine and leucine, upon the experimental animals, through evaluation of plasmatic level of some antioxidant enzymes. Material and Methods: The study was conducted on 32 male Wistar rats, which were fed with cholesterol, valine and leucine, for 60 days. The animals were divided into four groups, according to the received diet: the first group—standard diet;the second group—cholesterol (C);the third group—cholesterol and valine (C + V);the fourth group—cholesterol and leucine (C + L). Evaluations of the oxidative status, through plasma levels of the antioxidant enzymes: superoxide dismutase (SOD) and glutathione peroxidise (GPx), were made for the four mentioned groups of animals, at the beginning of the study (R0), after one (R1) and two months (R2). Results: The average values of SOD and GPx in group of animals fed exclusively with cholesterol (C) were significantly higher compared to the third group where cholesterol was supplemented with valine (C + V) or fourth group fed with cholesterol and leucine (C + L) (p < 0.001), after one month as well at the end of the experiment (two months). There were no significant differences in the levels of SOD and GPx between group III and group IV (p < 0.05) at the end of the experiment. Conclusion: Our results showed that valine and leucine decreased the serum levels of SOD and GPx and therefore they were useful antioxidants, which could improve the endothelial dysfunctions associated with atherosclerosis. Moreover, analysis of the oxidative status in the context of atherosclerotic mediated endothelial damage suggests that deviation from normal to alter endothelial status may be conditioned by an oxidants/antioxidants imbalance.

Increased leucine-rich repeats and immunoglobulin- like domains 1 expression enhances chemosensitivity in glioma

Leucine-rich repeats and immunoglobulin-like domains 1 （LRIG1） is an anti-oncogene. LRIG1 is correlated with Bcl-2 in ependymomas. Decreased Bcl-2 and manganese superoxide dismutase expression can improve the chemosensitivity of glioma. In the present study, a tissue microarray of human brain astrocytomas was constructed. To investigate the relationship of LRIG1 with Bcl-2 and manganese superoxide dismutase, LRIG1, Bcl-2 and manganese superoxide dismutase expression in our tissue microarray was determined using immunohistochemistry. In addition, we constructed the LRIG1-U251 cell line, and its responses to doxorubicin and temozolomide were detected using the MTT assay. Results showed that LRIG1 expression was significantly negatively correlated with Bcl-2 and manganese superoxide dismutase expression in glioma. Also, proliferation of LRIG1-U251 cells exposed to doxorubicin or temozolomide was significantly inhibited, i.e. in the LRIG1-U251 cell line, the chemosensitivity to doxorubicin and temozolomide was increased. This indicates that increased LRIG1 expression produces a chemosensitivity in glioma.

Genetic Analysis of Leucine Content in Indica-Japonica Hybrid Rice (Oryza sativa L.)

Genetic control of leucine content in indica-japonica hybrid rice (Oryza sativa L.) was studied in 35 crosses of F1 and F2 generations, which were derived from crossing 7 male sterile indica rice lines with 5 restorer japonica rice lines along with their parents. Two genetic models and their corresponding statistical methods for quantitative traits of triploid seeds in cereal crops were used for the analysis. The first was the unconditional genetic model, which refers to the analysis of cumulative measurements (from flowering to a specific time) along the developmental stages, while the second was the conditional genetic model, which relates to analysis from one developmental stage to another stage (t - 1→t). The results showed that leucine content of indica-japonica hybrid rice was controlled by the expression of triploid endosperm effect (endosperm additive effect and endosperm dominant effect), cytoplasm effect, diploid maternal plant effect (maternal additive effect and maternal dominant effect) and their environmental interaction effects. Of these effects, endosperm dominant effect and maternal dominant effect were more important at the earlier stages, while endosperm additive effect and maternal additive effect were more important at the later stages of rice grain development under both unconditional and conditional genetic analyses. Due to the high heritabilities, which came from endosperm, maternal and cytoplasm effects for leucine content at different developmental stages, selection for leucine content of indica-japonica hybrid rice would be more efficient at early generations in breeding programs.

Homeobox leucine zipper proteins and cotton improvement

Transcription factors play key roles in plant development and stress responses through their interaction with cis-elements and/or other transcription factors. Homeodomain associated leucine zipper proteins (HD-Zip) constitute a family of transcription factors that are characterized by the presence of a DNA-binding domain closely linked with leucine zipper motif functioning in dimer formation. This type of association is unique to plants and considered as an excellent candidate to activate developmental responses to altering environmental conditions. Cotton is the most important fiber plant with a lot of local and commercial uses in the world. HD-Zip proteins not only have key roles in different stages of vascular and inter-fascicular fiber differentiation of cotton but also are suggested to have an important role against abiotic stress that is one of the key factors limiting cotton productivity. Plants have developed various strategies to manage stress conditions through a combination of metabolic, physiological and morphological adaptations. These adaptive changes rely largely on alterations in gene expression. Therefore, transcriptional regulators play a crucial role in stress tolerance. Being a transcription factor HD-Zip might be a useful target for genetic engineering to generate multiple stress tolerance in susceptible plants. In the following chapter, we discussed how the HD-Zip proteins would play a useful role for cotton development both in fiber production and stress adaptation.

Synthesis and Physicochemical Properties of L-(+)-a-(Positive Butyl)-Leucine Ethyl Ester Chiral Ionic Liquids

L-（＋）-α-（positive butyl）-leucine ethyl ester bromide chiral ionic liquid was synthesized by using microwave-assisted synthesis method and L-（＋）-α-（positive butyl）-leucine ethyl ester terafluoroborate and hexafluorophosphate chiral ionic liquids were synthesized by the anion exchange reaction. The structures were characterized by IR, ~1HNMR and structure optimization calculation. The results of studies on physicochemical properties show that they possess better thermal stability, solubility, bio-solubility and high conductivity. They can serve as effective reaction media as well as chiral catalysts. They are presently being investigated as dispersion agents in molecular imprinting ployer.

Up-regulation of a homeodomain-leucine zipper gene HD-1 contributes to trichome initiation and development in cotton

Plant trichomes originate from epidermal cells.In this work,we demonstrated that a homeodomain-leucine zipper(HD-Zip)gene,Gh_A06G1283(Gh HD-1A),was related to the leaf trichome trait in allotetraploid cotton and could be a candidate gene for the T_1 locus.The ortholog of GhHD-1A in the hairless accession Gossypium barbadense cv.Hai7124 was interrupted by a long terminal repeat(LTR)retrotransposon,while GhHD-1A worked well in the hairy accession Gossypium hirsutum acc.T586.Sequence and phylogenetic analysis showed that GhHD-1A belonged to the HD-Zip IV gene family,which mainly regulated epidermis hair development in plants.Silencing of GhHD-1A and its homoeologs GhHD-1D in allotetraploid T586and Hai7124 could significantly reduce the density of leaf hairs and affect the expression levels of other genes related to leaf trichome formation.Further analysis found that GhHD-1A mainly regulated trichome initiation on the upper epidermal hairs of leaves in cotton,while the up-regulated expression of GhHD-1A in different organs/tissues also altered epidermal trichome development.This study not only helps to unravel the important roles of GhHD-1A in regulating trichome initiation in cotton,but also provides a reference for exploring the different forms of trichome development in plants.

Modifications of L-Glutamine and L-Leucine Transport in Proliferating Lymphocytes

Lymphocytes respond to mitogens that stimulate proliferation by increasing theirs metabolic activity. In this study we investigate L-Glutamine and L-Leucine uptake as markers of cell response to Concavalina A (ConcaA) stimulation, using a high-resolution flow technique. We found that lymphocytes induced to blast transformation enhanced rate and efficiency of amino acid uptake during cell proliferation. Considering that increases in transport is the first quantifiable response of cells during malignant transformation, amino acid uptake could also be useful as an early marker of malignancy.

Distribution，content and action site of leucine－enkephalin in pulmonary artery wall out of lung

When immunohistochemical method was used to investigate the distribution of peptidergic fibers in the pulmonary artery wall of SD rat, L-enkephalin immunoredetive (L-ENK) fibers were easily demonstrated. The contents of L-ENK in pulmonary artery of rat an

Discovery of a Novel Aminopeptidase N Inhibitor Dino-Leucine Borate

Aminopeptidase N(APN/CD13), a Zn2+-dependent ectopeptidase localized on the cell surface, is widely considered to influence the invasion of tumor cells. We found that boroleucine and dino-leucine borate exhibited a strong inhibitory effect on the enzyme activity of aminopeptidase N. The tested assay indicated that both compounds had an anti-proliferative effect on triple-negative breast cancer cells. Wound healing assay, migration test and matrigel-coated transwell assay showed that both boroleucine and dino-leucine borate inhibited the migration and invasion of breast cancer cells. Immunoblot analysis showed that both compounds down-regulated the expression of matrix metalloproteinase-2/9. In the capillary tube formation assay of human umbilical vein endothelial cells (HUVECs), dino-leucine borate showed better antiangiogenic activity than ubenimex even at a low concentration (10 μM). Moreover, compared with ubenimex, the anti-metastatic activity of dino-leucine borate in vivo was similar to or even better than that of ubenimex in the H22 pulmonary metastasis mouse model. In this paper, we found the novel APN inhibitors to markedly suppress the enzyme activity of APN and inhibit the migration and invasion of tumor cells in vitro and in vivo.