Enhanced Biotransformation of 2-Phenylethanol with Ethanol Oxidation in a Solid–Liquid Two-Phase System by Active Dry Yeast

2-Phenylethanol (2-PE) can be produced from l-phenylalanine (l-Phe) with the oxidation degradation of ethanol by active dry yeast. In this study, the catalysis effect of ethanol on biotransforming l-Phe into 2-PE by yeast was evaluated and optimized. The results indicated that increasing ethanol concentration was beneficial for enhancing 2-PE concentration but lowered the 2-PE productivity. Initial ethanol concentration above 25 g/l could strongly inhibit the 2-PE production. To obtain 2-PE with desirable concentrations with an economical operation mode, three fed-batch biotransformation operation methods using ethanol or/and glucose were carried out in a solid–liquid two-phase system. When using ethanol alone with the initial concentration of 10 g/l, the total concentration and overall productivity of 2-PE were 7.6 g/l and 0.065 g l⁻¹ h⁻¹, respectively. Furthermore, an experiment with controlled glucose solely (higher than 2 g/l) was finished. In this case, phenylacetaldehyde (PA) was detected along with ethanol accumulation, suggesting that reaction of PA → 2-PE in Ehrlich pathway was inhibited. To further enhance 2-PE production by using glucose only, a novel operation strategy to simultaneously control rates of glucose glycolysis and ethanol oxidative degradation with the aid of ISPR techniques was developed. With this strategy, 2-PE concentration and yield based on glucose consumption reached a higher level of 14.8 g/l and 0.12 g-PE/g-glucose, respectively, and these are the highest values reported up to date with the fed-batch biotransformation operation mode.     

空间环境诱发玉米细胞质雄性不育突变体的遗传分析

从返回式卫星"实践八号"搭载的08-641和18-599两份玉米自交系后代选育出3份雄性不育突变体,在不同地点、不同年份、不同季节进行种植观察,鉴定其育性表现,通过测交、反交及回交对不育性状的遗传特性进行分析。结果表明:3份不育突变材料均能稳定遗传,属可遗传的细胞质雄性不育类型。恢保关系测定和特异引物PCR扩增结果显示,3份不育材料均属玉米C型细胞质雄性不育类型,但3份不育材料在恢保关系上存在一定差异,推测它们可能分别属于玉米C型细胞质雄性不育的不同亚组。这些不育材料的发现,丰富了雄性不育胞质的遗传基础,在玉米不育化制种中具有一定应用价值。     

Impaired locomotor learning and altered cerebellar synaptic plasticity in pep-19/PCP4-null mice

PEP-19/PCP4 maps within the Down syndrome critical region and encodes a small, predominantly neuronal, IQ motif protein. Pep-19 binds calmodulin and inhibits calmodulin-dependent signaling, which is critical for synaptic function, and therefore alterations in Pep-19 levels may affect synaptic plasticity and behavior. To investigate its possible role, we generated and characterized pep-19/pcp4-null mice. Synaptic plasticity at excitatory synapses of cerebellar Purkinje cells, which express the highest levels of Pep-19, was dramatically altered in pep-19/pcp4-null mice. Instead of long-term depression, pep-19/pcp4-null mice exhibited long-term potentiation at parallel fiber-Purkinje cell synapses. The mutant mice have a marked deficit in their ability to learn a locomotor task, as measured by improved performance upon repeated testing on an accelerating rotarod. Thus, our data indicate that pep-19/pcp4 is a critical determinant of synaptic plasticity in cerebellum and locomotor learning.     

The B cell response is redundant and highly focused on V1V2 during early subtype C infection in a Zambian seroconverter

High-titer autologous neutralizing antibody responses have been demonstrated during early subtype C human immunodeficiency virus type 1 (HIV-1) infection. However, characterization of this response against autologous virus at the monoclonal antibody (MAb) level has only recently begun to be elucidated. Here we describe five monoclonal antibodies derived from a subtype C-infected seroconverter and their neutralizing activities against pseudoviruses that carry envelope glycoproteins from 48 days (0 month), 2 months, and 8 months after the estimated time of infection. Sequence analysis indicated that the MAbs arose from three distinct B cell clones, and their pattern of neutralization compared to that in patient plasma suggested that they circulated between 2 and 8 months after infection. Neutralization by MAbs representative of each B cell clone was mapped to two residues: position 134 in V1 and position 189 in V2. Mutational analysis revealed cooperative effects between glycans and residues at these two positions, arguing that they contribute to a single epitope. Analysis of the cognate gp120 sequence through homology modeling places this potential epitope near the interface between the V1 and V2 loops. Additionally, the escape mutation R189S in V2, which conferred resistance against all three MAbs, had no detrimental effect on virus replication in vitro. Taken together, our data demonstrate that independent B cells repeatedly targeted a single structure in V1V2 during early infection. Despite this assault, a single amino acid change was sufficient to confer complete escape with minimal impact on replication fitness.     

Engineering large fragment insertions into the chromosome of Escherichia coli

An effective DNA replacement system has been established for engineering large fragment insertions into the chromosome of Escherichia coli. The DNA replacement plasmid, pHybrid I, was first constructed based on the bacterial artificial chromosome (BAC) vector. Two fragments of the E. coli genome, 5.5 and 6.5 kb in length, were introduced into the vector for homologous recombination. In addition to the chloramphenicol gene, a second gene neo was introduced for double marker screening for recombinant clones. By shot-gun cloning and homologous recombination techniques, using our new recombinant vector (pHybrid I), a 20-kb fragment from Lactococcus lactis genomic DNA has been successfully integrated into the chromosome of the E. coli strain J93-140. Plating tests and PCR amplification indicated that the integration remained stable after many generations in cell culture. This system will be especially useful for the chromosome engineering of large heterologous fragment insertions, which is necessary for pathway engineering.     

长江流域水牛血液蛋白多态性研究

采集长江流域德昌、涪陵、江汉、滨湖和海子5个水牛地方品种共416 头牛的血样。电泳检测血红蛋白、血清运铁蛋白多态性,估算各等位基因频率及基因型频率,根据Hb及Tf两个位点的基因频率进行聚类分析。结果表明,5个水牛地方品种间遗传变异较小,其亲缘关系较近。     

New Isoflavonoid Glycosides from the Rhizomes of Iris leptophylla Lingelsh.

Two new isoflavonoid glucosides, 5-hydroxy-6,7-methylenedioxy-isoflavone-4＇-O-D-glucopyranosyl （2→〉l）-L-rhamnoside （irilone-bioside） （compound 1） and 5,4＇-methoxy-6,7-methylenedioxyisoflavone-3＇-O-β-D-glucoside （irisleptophyllidin） （compound 2）, together with five known compounds, nigricanin- 4＇-O-β-D-glucoside （compound 3）, irifloside （compound 4）, irigenin （compound 5）, 5, 3＇, 4＇-trimethoxy-6,7-methylenedioxyisoflavone （compound 6）, and nigricanin （compound 7） were isolated from the alcoholic extract of rhizomes of Iris leptophylla Lingelsh. Their structures were elucidated by spectroscopic methods.     

具有高再生性且对农杆菌敏感玉米自交系的筛选

以70个高代玉米自交系的幼胚为材料在NB培养基上进行离体培养,通过多次继代选择,从中筛选出了胚性愈伤组织诱导率高、克隆能力强的10个自交系,将这10个自交系的一部分胚性愈伤组织用作绿苗再分化,研究其再生能力;另一部分用农杆菌C58和GV3301转化,利用植物载体中携带的gus和g彦报告基因的瞬时表达为指标研究玉米基因型对农杆菌的敏感性。绿苗再分化结果表明,10个自交系都具有绿苗再分化能力,其中自交系6010、6038、6015、6051和6060的绿苗再分化力相对较高,分别为61．11％、31．94％、45％、33．33％和156．94％。gus瞬时表达率方差分析结果表明：玉米基因型对农杆菌C58的敏感性存在极显著差异,在自交系6034、6038的胚性愈伤组织上没有检测到gus瞬时表达,即这两个基因型对农杆菌C58不敏感,不能被其转化;其他7个基因型的平均gus瞬时表达率均大于70％,说明这7个基因型对农杆菌C58敏感。GFP荧光检测结果表明,在自交系6034、6038、6069和6010的胚性愈伤组织上没有检测到gyp瞬时表达,在其他6个自交系上检测到绿色荧光蛋白的表达。因此,认为自交系6015、6051和6060是对农杆菌GV3301敏感且具有高再生能力的玉米转基因受体材料;自交系6051、6010、6015、6060和6050是再生能力强且对农杆菌C58敏感的玉米转基因受体材料。     

LXRα is uniquely required for maximal reverse cholesterol transport and atheroprotection in ApoE-deficient mice

The liver X receptor (LXR) signaling pathway is an important modulator of atherosclerosis, but the relative importance of the two LXRs in atheroprotection is incompletely understood. We show here that LXRα, the dominant LXR isotype expressed in liver, plays a particularly important role in whole-body sterol homeostasis. In the context of the ApoE(-/-) background, deletion of LXRα, but not LXRβ, led to prominent increases in atherosclerosis and peripheral cholesterol accumulation. However, combined loss of LXRα and LXRβ on the ApoE(-/-) background led to an even more severe cholesterol accumulation phenotype compared to LXRα(-/-)ApoE(-/-) mice, indicating that LXRβ does contribute to reverse cholesterol transport (RCT) but that this contribution is quantitatively less important than that of LXRα. Unexpectedly, macrophages did not appear to underlie the differential phenotype of LXRα(-/-)ApoE(-/-) and LXRβ(-/-)ApoE(-/-) mice, as in vitro assays revealed no difference in the efficiency of cholesterol efflux from isolated macrophages. By contrast, in vivo assays of RCT using exogenously labeled macrophages revealed a marked defect in fecal sterol efflux in LXRα(-/-)ApoE(-/-) mice. Mechanistically, this defect was linked to a specific requirement for LXRα(-/-) in the expression of hepatic LXR target genes involved in sterol transport and metabolism. These studies reveal a previously unrecognized requirement for hepatic LXRα for optimal reverse cholesterol transport in mice.     

Genome sequence of the cycloprodigiosin-producing bacterial strain Pseudoalteromonas rubra ATCC 29570(T)

The cycloprodigiosin biosynthetic gene cluster has not been reported. We sequenced the genome of a cycloprodigiosin-producing bacterial strain, Pseudoalteromonas rubra ATCC 29570(T). Analysis revealed a probable cycloprodigiosin biosynthetic cluster, providing a good model for the study of cycloprodigiosin synthesis and regulation.