Investigations on Possible Roles of C-Terminal Propeptide of a Ca-Independent a-Amylase from Bacillus

( Salimi,Ali ),( Fatemeh Yousefi ),( Marzieh Ghollasi ),( Sara Daneshjou ),( Hesam Tavoli ),( Sirous Ghobadi ),( Khosro Khajch ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.8

Previously, an extracellular a-amylase (BKA) had been purified from the culture of Bacillus sp. KR8104. Subsequently, the crystal structure of the active enzyme revealed a 422 amino acids polypeptide. In this study, the bka was cloned into E. coli, which encoded a polypeptide of 659 amino acids including two additional fragments: one 44 residues N-terminal fragment and another 193 residues C-terminal fragment. In order to investigate the role of the C-terminal fragment, two constructs with and without this region [BKAΔ(N44) and BKAΔ(N44C193)] were designed and expressed in E. coli BL21. The optimum pH, thermal stability, and the end-products of starch hydrolysis were found to be similar in both constructs. The Km and Vmax values for BKAΔ (N44) were lower than BKAΔ (N44C193), using either starch or ethylidene-blocked 4-nitrophenylmaltoheptaoside as a substrate.

Seismic fragility analysis of seismically isolated nuclear power plants piping system

Salimi Firoozabad, E.,Jeon, B.G.,Choi, H.S.,Kim, N.S. North-Holland Pub. Co 2015 Nuclear engineering and design Vol.284 No.-

Nuclear power plants are high risk facilities due to the possibility of sudden seismic events, because any possible failure could initiate catastrophic radioactive contamination. The seismic fragility analysis of NPPs and related equipments (such as piping systems) is a proven method to determine their performance against any possible earthquake. In this study the Brookhaven National laboratory benchmark model of a piping system was considered for the fragility analysis. A tensile test was conducted to define the material properties. An initial seismic analysis of the piping system is performed to indicate the critical sections of the piping system. Numerical analysis was validated through a monotonic and cyclic loading experiment of two identified critical points of the piping system. The tests were conducted at the Korea Construction Engineering Development (KOCED) Seismic Simulation Test Center, Pusan National University, Korea. Fragility curves were expressed for critical points of the system as a function of the spectral acceleration of the records and the maximum relative displacement. The standard deviation of the response and capacity were calculated using mathematical formulas, assuming that those follow a log-normal distribution. We determined that the fragility curve of a pipe elbow must be derived for both the opening and closing mode, regarding the difference between the capacities of the elbow on those modes. The high confidence of low probability of failure for the considered fragility functions in a straight section in any direction is comparatively greater than the corresponding elbow section.

Lyapunov Based Adaptive-Robust Control of the Non-Minimum phase DC-DC Converters Using Input-Output Linearization

Salimi, Mahdi,Zakipour, Adel The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

In this research, a combined adaptive-robust current controller is developed for non-minimum-phase DC-DC converters in a wide range of operations. In the proposed nonlinear controller, load resistance, input voltage and zero interval of the inductor current are estimated using developed adaptation rules and knowing the operating mode of the converter for the closed-loop control is not required; hence, a single controller can be employed for a wide load and line changes in discontinuous and continuous conduction operations. Using the TMS320F2810 digital signal processor, the experimental response of the proposed controller is presented in different operating points of the buck/boost converter. During transition between different modes of the converter, the developed controller has a better dynamic response compared with previously reported adaptive nonlinear approach. Moreover, output voltage steady-state error is zero in different conditions.

Intrinsic origin of amyloid aggregation: Behavior of histidine (εεε) and (δδδ) tautomer homodimers of Aβ (1–40)

Salimi, Abbas,Li, Hao,Shi, Hu,Lee, Jin Yong Elsevier 2019 Biochimica et biophysica acta, General subjects Vol.1863 No.5

<P><B>Abstract</B></P> <P>Amyloid-beta protein (Aβ) accumulation in the brain, which is influenced by several factors, is a hallmark of Alzheimer's disease (AD). Despite the important role of histidine in stabilizing the fibrillar structure of the Aβ peptide at neutral pH, the effect of histidine tautomerism on Aβ peptide aggregation is still largely unknown. Histidine is in equilibrium between δ and ε tautomers and there are three histidine residues (H6, H13, and H14) in the Aβ(1–40) peptide. We performed molecular dynamics simulation on (δδδ) and (εεε) histidine tautomers with different initial homodimeric configurations to elucidate structural and aggregation features. Results indicate that (εεε) homodimers have very low propensity or almost no tendency to form β-sheets, whereas (δδδ) dimers predominantly form β-sheets due to interactions between central hydrophobic core (CHC) residues and C-terminal residues. β-sheet formation occurred in the same regions of each dimer chain at the CHC and C-/N- terminals for different configurations of (δδδ). These results suggest that (δδδ) has an important role in AD progression. Our study provides deeper insight into the effect of tautomerism of histidine residues in Aβ(1–40) on amyloid aggregation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> (εεε) tautomers show low propensity to form β-sheets during homodimerization. </LI> <LI> (δδδ) tautomers show high β-sheets amount during homodimerization. </LI> <LI> (δδδ) tautomers may play more important role than (εεε) in Alzheimer. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Xylene Induces Oxidative Stress and Mitochondria Damage in Isolated Human Lymphocytes

Salimi, Ahmad,Talatappe, Behnaz Shoja,Pourahmad, Jalal Korean Society of ToxicologyKorea Environmental Mu 2017 Toxicological Research Vol.33 No.3

Xylene is a cyclic hydrocarbon and an environmental pollutant. It is also used in medical technology, paints, dyes, polishes and in many industries as a solvent; therefore, an understanding of the interaction between xylene and human lymphocytes is of significant interest. Biochemical assessment was used to demonstrate that exposure of lymphocytes to xylene induces cytotoxicity (at 6 hr), generates intracellular reactive oxygen species, collapse of mitochondrial membrane potential, lysosomal injury, lipid peroxidation and depletion of glutathione (at 3 hr). The findings show that xylene triggers oxidative stress and organelle damage in lymphocytes. The results of our study suggest that the use of antioxidant, mitochondrial and lysosomal protective agents can be helpful for individuals subject to chronic exposure to xylene.

Improving Collision Energy Absorption In High Speed Train By Using Thin Walled Tubes

Salimi, Ehsan,Molatefi, Habib,Rezvani, MohammadAli,Shahsavari, Erfan The Korean Society for Railway 2013 International Journal of Railway Vol.6 No.3

The purpose of this paper is investigating the effect and influence rates of utilizing thin walled energy absorption tubes for improving crashworthiness parameter by increasing energy absorption of the body in high speed railcars. In order to find this, a proper profile of available tubes is chosen and added to the structure of selected high speed train in Iranian railway network (Pardis Trainset) and then examined in the scenario of impact with other moving rolling stock. Because of the specific features of LS-DYNA 3D software at collision analysis, the dynamic simulation has been performed in LS-DYNA 3D. The results of the analysis clearly indicate the improvement of train crashworthiness as the energy absorption of structure increases more than 30 percent in comparison with the original body. This strategy delays and reduces the shock to the structure. The verification of the simulation is by using ECE R66 standard.

Efficacy of Primed In Situ Labelling in Determination of HER-2 Gene Amplification and CEN-17 Status in Breast Cancer Tissue

Salimi, Mahdieh,Mozdarani, Hossein,Majidzadeh-A, Keivan Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.1

Considerable attention has been given to the accuracy of HER-2 testing and the correlation between the results of different testing methods. This interest reflects the growing importance of HER-2 status in the management of patients with breast cancer. In this study the detection of HER-2 gene and centromere 17 status was evaluated using dual-colour primed in situ labelling (PRINS) in comparison with fluorescence in situ hybridization (FISH). These two methods were evaluated on a series of 27 formalin fixed paraffin embedded breast carcinoma tumours, previously tested for protein overexpression by HercepTest (grouped into Hercep 1+/0, 2+ and 3+). HER-2 gene amplification (ratio${\geq}2.2$) by PRINS was found in 3:3, 6:21 and 0:3 in IHC 3+, 2+ and 1+/0 cases, respectively. Comparing FISH and IHC (immunohistochemistry), showed the same results as for PRINS and IHC. Chromosome 17 aneusomy was found in 10 of 21 IHC 2+ cases (47.6%), of which 1 (10%) showed hypodisomy (chromosome 17 copy number per cell${\leq}1.75$), 7 (70%) showed low polysomy (chromosome 17 copy number per cell=2.26 - 3.75) and 2 (20%) showed high polysomy (chromosome 17 copy number per cell ${\geq}3.76$). The overall concordance of detection of HER-2 gene amplification by FISH and PRINS was 100% (27:27). Furthermore, both the level of HER-2 amplification and copy number of CEN17 analysis results correlated well between the two methods. In conclusion, PRINS is a reliable, reproducible technique and in our opinion can be used as an additional test to determine HER-2 status in breast tumours.

Reliability-based fragility analysis of nonlinear structures under the actions of random earthquake loads

Salimi, Mohammad-Rashid,Yazdani, Azad Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.1

This study presents the reliability-based analysis of nonlinear structures using the analytical fragility curves excited by random earthquake loads. The stochastic method of ground motion simulation is combined with the random vibration theory to compute structural failure probability. The formulation of structural failure probability using random vibration theory, based on only the frequency information of the excitation, provides an important basis for structural analysis in places where there is a lack of sufficient recorded ground motions. The importance of frequency content of ground motions on probability of structural failure is studied for different levels of the nonlinear behavior of structures. The set of simulated ground motion for this study is based on the results of probabilistic seismic hazard analysis. It is demonstrated that the scenario events identified by the seismic risk differ from those obtained by the disaggregation of seismic hazard. The validity of the presented procedure is evaluated by Monte-Carlo simulation.

Reactive blending of polylactic acid/polyethylene glycol toward biodegradable film

Ali Salimi,Shervin Ahmadi,Mona Faramarzi,Jalal Faghihi 한국고분자학회 2023 Macromolecular Research Vol.31 No.9

Polyethylene glycol (PEG) was first modified with bis(trimethoxysilylpropyl) amine as an effective coupling agent. Different compositions of PEG and polylactic acid (PLA) were then prepared through melt blending. The silane modification of PEG was confirmed by infrared spectroscopy. The SEM micrographs of different PEG/PLA compositions showed rather homogenous single phase morphology in the compositions with silane-modified PEG. The efficacy of silane-modified PEG maybe due to interfacial compatibilization of PLA and the silane-modified PEG. According to TGA and DSC thermograms, the PEG loading into PLA resulted in somewhat higher thermal stability and increase in the degree of crystallinity of up to 52%. The dynamic mechanical thermal analysis showed lower glass transition temperatures and higher toughness for all the silane-modified PEG/PLA compositions than that of the neat PLA. The biodegradation behavior of silane-modified PEG/PLA compositions increased linearly as evidenced by material weight loss either in water absorption or fungi associated destruction tests.

Lyapunov Based Adaptive-Robust Control of the Non-Minimum phase DC-DC Converters Using Input–Output Linearization

Mahdi Salimi,Adel Zakipour 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

In this research, a combined adaptive-robust current controller is developed for non-minimum-phase DC–DC converters in a wide range of operations. In the proposed nonlinear controller, load resistance, input voltage and zero interval of the inductor current are estimated using developed adaptation rules and knowing the operating mode of the converter for the closed-loop control is not required; hence, a single controller can be employed for a wide load and line changes in discontinuous and continuous conduction operations. Using the TMS320F2810 digital signal processor, the experimental response of the proposed controller is presented in different operating points of the buck/boost converter. During transition between different modes of the converter, the developed controller has a better dynamic response compared with previously reported adaptive nonlinear approach. Moreover, output voltage steady-state error is zero in different conditions.