Engineering of formate dehydrogenase for improving conversion potential of carbon dioxide to formate.

Formate dehydrogenase (FDH) is a D-2-hydroxy acid dehydrogenase, which can reversibly reduce CO2 to formate and thus act as non-photosynthetic CO2 reductase. In order to increase catalytic efficiency of formate dehydrogenase for CO2 reduction, two mutants V328I/F285W and V354G/F285W were obtained of which reduction activity was about two times more than the parent CbFDHM2, and the formate production from CO2 catalyzed by mutants were 2.9 and 2.7-fold higher than that of the parent CbFDHM2. The mutants had greater potential in CO2 reduction. The optimal temperature for V328I/F285W and V354G/F285W was 55 °C, and they showed increasement of relative activity under 45 °C to 55 °C compared with parent. The optimal pH for the mutants was 9.0, and they showed excellent stability in pH 4.0-11.5. The kcat/Km values of mutants were 1.75 times higher than that of the parent. Then the molecular basis for its improvement of biochemical characteristics were preliminarily elucidated by computer-aided methods. All of these results further established a solid foundation for molecular modification of formate dehydrogenase and CO2 reduction.

Compound heterozygous mutations in PMFBP1 cause acephalic spermatozoa syndrome: A case report.

BACKGROUND: Acephalic spermatozoa syndrome (ASS) is an extremely rare form of severe teratozoospermia, where in most of the sperm either appear to lack heads or have disconnected or poorly connected heads and tails. CASE SUMMARY: We reported the case of a male patient with secondary infertility whose sperm showed typical ASS upon morphological analysis. Whole-exome sequencing was performed on the patient's peripheral blood, which revealed two heterozygous variants of the PMFBP1 gene: PMFBP1c.414+1G>T (p.?) and PMFBP1c.393del (p.C132Afs*3). CONCLUSION: It is speculated that the compound homozygous mutation of PMFBP1 may be the cause of ASS. We conducted a literature review in order to provide the basis for genetic counseling and clinical diagnosis of patients with ASS.

[Application of single-sperm sequencing technology in preimplantation genetic testing for men with autosomal dominant polycystic kidney disease].

OBJECTIVE: To investigate the value of single-sperm sequencing technology in preimplantation genetic testing. METHODS: Haplotypes were constructed by single-sperm isolation combined with single-sperm sequencing for a patient with autosomal dominant polycystic kidney disease (ADPKD) caused by de novo mutation of the PKD1 gene c.3815T>G. 50. Single-sperm samples were isolated by mechanical braking, whole-genome amplification was performed, and mutation loci and their 187 upstream and downstream single nucleotide polymorphisms (SNP) were designed. The amplified products were verified for determination of the chromosome haplotypes carrying or not carrying pathogenic mutations. The embryos carrying pathogenic mutations were identified in 7 embryonic trophectoderm cell biopsy samples by high-throughput sequencing after whole-genome amplification. Available blastocysts were selected for embryo transfer, and amniotic fluid samples were collected at 18 weeks of gestation to determine whether the fetuses carried pathogenic mutations. RESULTS: A total of 30 SNPs were identified by single-sperm sequencing, and haplotypes were successfully constructed. Preimplantation haplotype analysis indicated that 5 embryos carried pathogenic mutations and 2 did not. mid-gestation amniotic fluid genetic testing revealed no PKD1 gene c.3815T>G mutation in the fetuses. CONCLUSION: SNPs can be identified by single-sperm sequencing in males carrying de novo pathogenic mutation, and haplotypes can be constructed by linkage analysis for preimplantation genetic testing of embryos.

Steering Metal-Organic Network Structures through Conformations and Configurations on Surfaces.

Molecular adsorption conformations and arrangement configurations on surfaces are important structural aspects of surface stereochemistry, but their roles in steering the structures of metal-organic networks (MONs) remain vague and unexplored. In this study, we constructed MONs by the coordination self-assembly of isocyanides on Cu(111) and Ag(111) surfaces and demonstrated that the MON structures can be steered by surface stereochemistry, including the adsorption conformations of the isocyanide molecules and the arrangement configurations of the coordination nodes and subunits. The coordination self-assembly of 1,4-phenylene diisocyanobenzene afforded a honeycomb MON consisting of 3-fold (isocyano)3-Cu motifs on a Cu(111) surface. In contrast, geometrically different chevron-shaped 1,3-phenylene diisocyanobenzene (m-DICB) failed to generate a MON, which is ascribable to its standing conformation on the Cu(111) surface. However, m-DICB was adsorbed in a flat conformation on a Ag(111) surface, which has a larger lattice constant than a Cu(111) surface, and smoothly underwent coordination self-assembly to form a MON consisting of (isocyano)3-Ag motifs. Interestingly, only C3-Ag nodes with heterotactic configurations could grow into larger subunits; those subunits with heterotactic configurations further grew into Sierpinski triangle fractals (up to fourth order), while subunits with homotactic configurations afforded a triangular MON.

Expression of Novel L-Leucine Dehydrogenase and High-Level Production of L-Tert-Leucine Catalyzed by Engineered Escherichia coli.

Leucine dehydrogenase (LDH) is a NAD+-dependent oxidoreductase, which can selectively catalyze α-keto acids to obtain α-amino acids and their derivatives. It plays a key role in the biosynthesis of L-tert-leucine (L-Tle). As a non-naturally chiral amino acid, L-Tle can be used as an animal feed additive, nutrition fortifier, which is a perspective and important building block in the pharmaceutical, cosmetic, and food additive industry. In this study, four hypothetical leucine dehydrogenases were discovered by using genome mining technology, using the highly active leucine dehydrogenase LsLeuDH as a probe. These four leucine dehydrogenases were expressed in Escherichia coli BL21(DE3), respectively, and purified to homogeneity and characterized. Compared with the other enzymes, the specific activity of PfLeuDH also shows stronger advantage. In addition, the highly selective biosynthesis of L-Tle from trimethylpyruvic acid (TMP) was successfully carried out by whole-cell catalysis using engineered E. coli cells as biocatalyst, which can efficiently coexpress leucine dehydrogenase and formate dehydrogenase. One hundred-millimolar TMP was catalyzed for 25 h, and the yield and space-time yield of L-Tle reached 87.38% (e.e. >99.99%) and 10.90 g L-1 day-1. In short, this research has initially achieved the biosynthesis of L-Tle, laying a solid foundation for the realization of low-cost and large-scale biosynthesis of L-Tle.

On-surface synthesis of planar dendrimers via divergent cross-coupling reaction.

Dendrimers are homostructural and highly branched macromolecules with unique dendritic effects and extensive use in multidisciplinary fields. Although thousands of dendrimers have been synthesized in solution, the on-surface synthetic protocol for planar dendrimers has never been explored, limiting the elucidation of the mechanism of dendritic effects at the single-molecule level. Herein, we describe an on-surface synthetic approach to planar dendrimers, in which exogenous palladium is used as a catalyst to address the divergent cross-coupling of aryl bromides with isocyanides. This reaction enables one aryl bromide to react with two isocyanides in sequential steps to generate the divergently grown product composed of a core and two branches with high selectivity and reactivity. Then, a dendron with four branches and dendrimers with eight or twelve branches in the outermost shell are synthesized on Au(111). This work opens the door for the on-surface synthesis of various planar dendrimers and relevant macromolecular systems.

On-surface reactions of aryl chloride and porphyrin macrocycles via merging two reactive sites into a single precursor.

The reaction of aryl chloride and porphyrin macrocycles, which are merged into a single precursor, has been achieved on Cu(111). Scanning tunneling microscopy analysis of the oligomer products showed that the adjacent porphyrin moieties linked mainly by the phenyl group with the porphyrin macrocycle.

On-surface synthesis of poly(p-phenylene ethynylene) molecular wires via in situ formation of carbon-carbon triple bond.

The carbon-carbon triple bond (-C≡C-) is an elementary constituent for the construction of conjugated molecular wires and carbon allotropes such as carbyne and graphyne. Here we describe a general approach to in situ synthesize -C≡C- bond on Cu(111) surface via homo-coupling of the trichloromethyl groups, enabling the fabrication of individual and arrays of poly(p-phenylene ethynylene) molecular wires. Scanning tunneling spectroscopy reveals a delocalized electronic state extending along these molecular wires, whose structure is unraveled by atomically resolved images of scanning tunneling microscopy and noncontact atomic force microscopy. Combined with density functional theory calculations, we identify the intermediates formed in the sequential dechlorination process, including surface-bound benzyl, carbene, and carbyne radicals. Our method overcomes the limitation of previous on-surface syntheses of -C≡C- incorporated systems, which require the precursors containing alkyne group; it therefore allows for a more flexible design and fabrication of molecular architectures with tailored properties.

[Characteristics and affecting factors of sap flow density of Pinus tabuliformis and Hippophae rhamnoides in growing season in the hilly region of the Loess Plateau, China]. / é»„åœŸä¸˜é™µåŒºæ²¹æ¾ã€æ²™æ£˜ç”Ÿé•¿æ—ºç››æœŸæ ‘å¹²æ¶²æµå¯†åº¦ç‰¹å¾åŠå ¶å½±å“å› ç´ .

The dynamic changes of sap flow density (Js) of Pinus tabuliformis and Hippophae rhamnoides in plantations from July to September in 2015 was monitored through thermal dissipation probe in the hilly region of the Loess Plateau. In addition, plant physiological characteristics were analyzed to determine the water use types of these two species. The results indicated that the daily changes of Js of P. tabuliformis and H. rhamnoides showed a single peak during both pre- and post-precipitation. The Js of P. tabuliformis in growing season (12.62 mL·m-2·s-1) was significantly higher than that of H. rhamnoides (2.60 mL·m-2·s-1). The Js of these two species were significantly positively correlated with photosynthetic active radiation, vapor pressure deficit, soil volume-tric water content (SWC). The Js of these two species were mainly influenced by meteorological factors during pre- and post-precipitation in both August and September. The contribution of SWC to Js of H. rhamnoides increased by 4.2% after precipitation in September, but the contribution of SWC to Js of P. tabuliformis decreased by 0.3% after precipitation in both August and September, respectively. Meanwhile, P. tabuliformis showed significantly higher water potential in midday leaf, but lower coefficient of variation (7.3%) than H. rhamnoides with the coefficient of variation of 11.7%. However, H. rhamnoides exhibited higher leaf stomatal conductance. Thus, P. tabuliformis and H. rhamnoides could be considered as isohydry and anisohydry species, respectively.

Aldehyde Dehydrogenase Gene Superfamily in Populus: Organization and Expression Divergence between Paralogous Gene Pairs.

Aldehyde dehydrogenases (ALDHs) constitute a superfamily of NAD(P)+-dependent enzymes that catalyze the irreversible oxidation of a wide range of reactive aldehydes to their corresponding nontoxic carboxylic acids. ALDHs have been studied in many organisms from bacteria to mammals; however, no systematic analyses incorporating genome organization, gene structure, expression profiles, and cis-acting elements have been conducted in the model tree species Populus trichocarpa thus far. In this study, a comprehensive analysis of the Populus ALDH gene superfamily was performed. A total of 26 Populus ALDH genes were found to be distributed across 12 chromosomes. Genomic organization analysis indicated that purifying selection may have played a pivotal role in the retention and maintenance of PtALDH gene families. The exon-intron organizations of PtALDHs were highly conserved within the same family, suggesting that the members of the same family also may have conserved functionalities. Microarray data and qRT-PCR analysis indicated that most PtALDHs had distinct tissue-specific expression patterns. The specificity of cis-acting elements in the promoter regions of the PtALDHs and the divergence of expression patterns between nine paralogous PtALDH gene pairs suggested that gene duplications may have freed the duplicate genes from the functional constraints. The expression levels of some ALDHs were up- or down-regulated by various abiotic stresses, implying that the products of these genes may be involved in the adaptation of Populus to abiotic stresses. Overall, the data obtained from our investigation contribute to a better understanding of the complexity of the Populus ALDH gene superfamily and provide insights into the function and evolution of ALDH gene families in vascular plants.