37 research outputs found
Purification of an alpha amylase from Aspergillus flavus NSH9 and molecular characterization of its nucleotide gene sequence
In this study, an alpha-amylase enzyme from a locally isolated Aspergillus flavus NSH9 was purified and characterized. The extracellular α-amylase was purified by ammonium sulfate precipitation and anion-exchange chromatography at a final yield of 2.55-fold and recovery of 11.73%. The molecular mass of the purified α-amylase was estimated to be 54 kDa using SDS-PAGE and the enzyme exhibited optimal catalytic activity at pH 5.0 and temperature of 50 °C. The enzyme was also thermally stable at 50 °C, with 87% residual activity after 60 min. As a metalloenzymes containing calcium, the purified α-amylase showed significantly increased enzyme activity in the presence of Ca2+ ions. Further gene isolation and characterization shows that the α-amylase gene of A. flavus NSH9 contained eight introns and an open reading frame that encodes for 499 amino acids with the first 21 amino acids presumed to be a signal peptide. Analysis of the deduced peptide sequence showed the presence of three conserved catalytic residues of α-amylase, two Ca2+-binding sites, seven conserved peptide sequences, and several other properties that indicates the protein belongs to glycosyl hydrolase family 13 capable of acting on α-1,4-bonds only. Based on sequence similarity, the deduced peptide sequence of A. flavus NSH9 α-amylase was also found to carry two potential surface/secondary-binding site (SBS) residues (Trp 237 and Tyr 409) that might be playing crucial roles in both the enzyme activity and also the binding of starch granules. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature
Experimental investigation and theoretical calculation of 3He-particle induced nuclear reactions on cadmium up to 27MeV
Excitation functions of 3He-particle induced nuclear reactions on natural cadmium were measured using the standard stacked foil technique and high resolution gamma-ray spectroscopy. From their threshold energies up to 27 MeV, cross-sections for natCd(3He,xn)117m,113,111,110Sn, natCd(3He,xnp)117m,g,116m,115m,114m,113m,111,110m,g,109,108,107In, and natCd(3He,X)115g,111mCd reactions were measured. The nuclear codes TALYS, and EMPIRE-3,1 were used to describe the formation of these products. The present data were compared to theoretical results and to the available experimental data. Integral yields for some important radioisotopes were determined
Experimental investigation and theoretical calculation for 3He induced nuclear reactions on vanadium
Using stacked-foil activation technique and gamma-ray spectrometry, excitation functions for 3He induced
nuclear reactions on natV were measured. Cross-sections for natV(3He,xn)52m,gMn and natV(3He,pxn)51Cr
nuclear reactions were measured up to 27 MeV utilizing the MGC-20E cyclotron of ATOMKI. The measurements
establish for the first time consistent excitation curves. Comparisons with results for values derived
from different theoretical codes were included. Integral yield were calculated
Activation cross-section data for α-particle-induced nuclear reactions on natural vanadium for practical applications
Excitation functions for α-induced reactions on natural vanadium were measured in the energy range
up to 20 MeV. The stacked-foil activation technique was used. The experimental results were compared with the
theoretical calculations using EMPIRE-3.1, EMPIRE-3.2.2 and TENDL 2015, and with earlier experimental results.
Thick target yields were calculated for the production of 54Mn and for the associated impurity 52M
Measurement and theoretical analysis of the excitation functions for 3He induced reactions on natSn
Excitation functions of 3He induced nuclear reactions on natSn were measured up to 26 MeV using the
stacked-foil technique, utilizing the MGC-20E cyclotron of ATOMKI. Using HPGe detector the following
radioisotopes were identified: 116,117,118,119g,119m,121g,121m,123mTe, 115g,116m,117,118m,120m,122g,124gSb and
113g,117mSn. The experimental results are presented for the first time in this energy range. The results
of theoretical calculations based on EMPIRE and TENDL library were compared with the present data.
Integral yields for some isotopes were calculated