Molecular cloning and characterization of 3-methylcrotonyl-CoA carboxylase from soybean

A cDNA clone and genes coding for the 85 kDa biotin-containing polypeptide of soybean has been isolated and sequenced. This 85 kDa polypeptide has been identified as the biotin-containing subunit of 3-methylcrotonyl-CoA carboxylase (MCCase). This is the first plant gene coding for a biotin-containing enzyme to be cloned. It is also the first time that the primary sequence of the biotin-containing subunit of MCCase has been determined;The deduced amino acid sequence of the biotin-containing subunit of MCCase of soybean shows high homology with other known biotin-containing enzymes. Amino acid sequence homology between the soybean MCCase and other biotin enzymes identified the biotin carboxylase and the biotin carboxyl carrier domains. In addition, the first 21 amino acid residues have the characteristics of a mitochondrial targeting signal peptide. The cleavage site of the signal peptide of the soybean biotin-containing subunit of MCCase has been confirmed by the direct sequencing of the N-terminus of the mature protein;Soybean MCCase has been purified to near homogeneity by a five step purification procedure. The purified MCCase is composed of equal proportions of a 85 kDa biotin-containing subunit and a 59 kDa biotin-free subunit, with a molecular weight of approximately 970,000 ± 83,000. Soybean MCCase appears to have an [alpha][subscript]6[beta][subscript]6 quaternary structure;Initial velocity kinetic studies of soybean MCCase with competitive inhibitors demonstrated that soybean MCCase follows a random Bi Bi Uni Uni Ping Pong mechanism;Putative isozymes of the soybean MCCase have been discovered for the first time. Isoform I is more active and has a lower K[subscript] m for ATP compared to isoform II. The K[subscript] ms for HCO[subscript]3[superscript]- and 3-methylcrotonyl-CoA (Mc-CoA) are similar for both forms. The molecular weight of the native isoforms are the same, and they possess biotin-containing subunits of identical molecular weights;The effect of development on MCCase activity and accumulation of the biotin subunit and mRNA coding for this subunit have been examined. The results are consistent with the presumed role of this enzyme in leucine catabolism, namely, MCCase is highly expressed in tissues that need to generate ATP and reducing equivalents via respiration of organic constituents

The Nonlinear Talbot Effect of Rogue Waves

Akhmediev and Kuznetsov-Ma breathers are rogue wave solutions of the nonlinear Schr\"odinger equation (NLSE). Talbot effect (TE) is an image recurrence phenomenon in the diffraction of light waves. We report the nonlinear TE of rogue waves in a cubic medium. It is different from the linear TE, in that the wave propagates in a NL medium and is an eigenmode of NLSE. Periodic rogue waves impinging on a NL medium exhibit recurrent behavior, but only at the TE length and at the half-TE length with a \pi-phase shift; the fractional TE is absent. The NL TE is the result of the NL interference of the lobes of rogue wave breathers. This interaction is related to the transverse period and intensity of breathers, in that the bigger the period and the higher the intensity, the shorter the TE length.Comment: 4 pages, 4 figure

Influences of Geometric Parameters upon Nozzle Performances in Scramjets

AbstractThis article investigates and presents the influences of geometric parameters of a scramjet exerting upon its nozzle performances. These parameters include divergent angles, total lengths, height ratios, cowl lengths, and cowl angles. The flow field within the scramjet nozzle is simulated numerically by using the CFD software—FLUENT in association with coupled implicit solver and an RNG k-ɛ turbulence model

Quartz sand surface morphology of granitic tafoni at Laoshan, China

43-48In this study, a SEM method was used to analyze the surface morphology of the quartz sand granitic tafoni at Laoshan, for the purpose of exploring the weathering process of this tafoni. Present study showed that granitic tafoni at Laoshan, the quartz sand roundness was dominated by angular and sub-angular morphologies. Massive Hydrodynamic features had been developed on the quartz sand surfaces, as well as wind and chemistry forms, which were more developed. It was determined that granitic tafoni at Laoshan, the quartz sand had suffered long-term rainy and windy mechanical erosion, as well as chemical dissolution from residual pit water. These findings differed from the earlier views that the tafone was formed by the glacial melt water