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Synthesis and Pharmacological Studies on a Cyclooligopeptide from Marine Bacteria

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Chinese Journal of Chemistry 2011年第9期29卷 1911-1916页

作者： rajiv, dahiya Hemendra, Gautam Department of Pharmaceutical Chemistry Globus College of Pharmacy Bhojpur Road Bhopal-462 045 Madhya Pradesh India Department of Pharmacology Institute of Pharmacy Invertis University Bareilly-243 123 Uttar Pradesh India

A natural proline-rich tetrapeptide cyclo-prolyl-leucyl-prolyl-phenylalanyl was prepared employing solu- tion-phase method of peptide synthesis through coupling of dipeptide fragments Boc-l-Pro-l-Leu-OH and 1-Pro-l-Phe-OMe which utilizes diisopropylcarbodiimide （DIPC） as coupling agent and N-methylmorpholine （NMM） as the base. Deprotection of linear tetrapeptide unit followed by its cyclization provided a cyclopeptide, identical in all aspects to the natural molecule. Pharmacological evaluation showed cytotoxic, antifungal and antihelmintic po- tential of synthesized peptide against Dalton＇s Lymphoma Ascites （DLA） and Ehrlich＇s Ascites Carcinoma （EAC） cell lines, pathogenic dermatophytes and earthworms.

关键词： marine bacteria natural product solution phase synthesis peptides biological activity cytotoxicity

Synthetic and biological studies on a cyclopolypeptide of plant origin

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2008年第5期9卷 391-400页

作者： rajiv dahiya Akhilesh KUMAR Department of Pharmaceutical Chemistry Rajiv Academy for Pharmacy

Objective:A natural cyclic peptide previously isolated from Citrus medica was synthesized by coupling of tetrapep-tide units Boc-Leu-Pro-Trp-Leu-OMe and Boc-Ile-Ala-Ala-Gly-OMe after proper deprotection at carboxyl and amino terminals followed by cyclization of linear octapeptide segment. Methods:Solution phase technique was adopted for the synthesis of cyclooctapeptide-sarcodactylamide. Required tetrapeptide units were prepared by coupling of Boc-protected dipeptides viz. Boc-Leu-Pro-OH and Boc-Ile-Ala-OH with respective dipeptide methyl esters Trp-Leu-OMe and Ala-Gly-OMe. Cyclization of linear octapeptide unit was done by p-nitrophenyl ester method. The structure of synthesized cyclopolypeptide was elucidated by FTIR,1H NMR,13C NMR,FABMS spectral data and elemental analysis. The newly synthesized peptide was evaluated for dif-ferent pharmacological activities including antimicrobial,anthelmintic and cytotoxic activities. Results:Synthesis of sarcodac-tylamide was accomplished with >78% yield utilizing dicyclohexylcarbodiimide(DCC) as coupling agent. Newly synthesized peptide possessed potent cytotoxic activity against Dalton's lymphoma ascites(DLA) and Ehrlich's ascites carcinoma(EAC) cell lines,in addition to moderate anthelmintic activity against earthworms Megascoplex konkanensis,Pontoscotex corethruses and Eudrilus sp. Moreover,cyclopolypeptide displayed good antimicrobial activity against pathogenic fungi Candida albicans and Gram-negative bacteria Pseudomonas aeruginosa,in comparison to standard drugs griseofulvin and ciprofloxacin. Conclusion:Solution phase technique employing DCC and triethylamine(TEA) as base proved to be effective for the synthesis of natural cyclooctapeptide. N-methyl morpholine(NMM) was found to be a better base for the cyclization of linear octapeptide unit in comparison to TEA and pyridine.

关键词： Cyclic octapeptide Citrus medica var. sarcodactylis Sarcodactylamide Peptide synthesis Anthelmintic activity Antimicrobial activity Cytotoxicity

Hydrothermal synthesis of Zn-Mg-based layered double hydroxide coatings for the corrosion protection of copper in chloride and hydroxide media

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International Journal of Minerals,Metallurgy and Materials 2021年第12期28卷 1991-2000页

作者： Nikhil Gopal Ji rajiv Prakash School of Materials Science and Technology Indian Institute of Technology(BHU)VaranasiVaranasi-221005Uttar PradeshIndia Centre for advanced studies Dr.APJAKTU LucknowU.P.-226031India

Layered double hydroxides(LDHs)hinder corrosive elements by forming a double layer and locking them between its ***,LDHs are interesting materials in corrosion *** this work,Zn-Mg-based LDHs are grown over a copper substrate by using a hydrothermal *** types of Zn-Mg-based LDH coating are prepared based on hydrothermal reaction *** types are characterized through Fourier transform infrared spectroscopy,Raman spectroscopy,high-resolution scanning electron microscopy,energy dispersive X-ray analysis,atomic force microscopy,and X-ray *** show that the two types of LDH coating are successfully grown on copper;however,they differ in thickness and structural *** testing of the LDH coatings is executed in 0.1 M Na Cl and 0.1 M Na OH through alternating current impedance measurements and Tafel polarization *** show that L48 gives more than 90%protection to copper,which is higher than the protection provided by ***,both LDH coatings(L24 and L48)are more effective corrosion inhibitors in Na Cl than in Na OH,suggesting that the LDH coatings can more efficiently exchange Cl ions than OH ions.

关键词： corrosion coating copper

Optical anisotropy and the direction of polarization of exciton emissions in a semiconductor quantum dot:Effect of heavy-and light-hole mixing

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Chinese Physics B 2017年第8期26卷 400-406页

作者： Ranber Singh rajiv Kumar Vikramjeet Singh Department of Physics Sri Guru Gobind Singh CollegeSector 26Chandigarh 160019India Department of Physics DAV University JalandharPunjab 144012India IKGPTU Campus HoshiarpurPunjab 146001India

The dependence of the directions of polarization of exciton emissions, fine structure splittings （FSS）, and polarization anisotropy on the light- and heavy-hole （LH-HH） mixing in semiconductor quantum dots （QDs） is investigated using a mesoscopic model. In general, all QDs have a four-fold exciton ground state. Two exciton states have directions of polarization in the growth-plane, while the other two are along the growth direction of the QD. The LH-HH mixing does affect the FSS and polarization anisotropy of bright exciton states in the growth-plane in the low symmetry QDs （e.g., C2v, CS, C1 ）, while it has no effect on the FSS and polarization anisotropy in high symmetry QDs （e.g., C3V, D2d）. When the hole ground state is pure HH or LH, the bright exciton states in the growth-plane are normal to each other. The LH-HH mixing affects the relative intensities and directions of bright exciton states in the growth-plane of the QD. The polarization anisotropy of exciton emissions in the growth-plane of the QD is independent of the phase angle of LH-HH mixing but strongly depends on the magnitude of LH-HH mixing in low symmetry QDs.

关键词： light-heavy hole mixing excitons quantum dots

Estimating the impact of antiretroviral therapy on HIV-TB co-infection:Optimal strategy prediction

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International Journal of Biomathematics 2021年第1期14卷 175-221页

作者： Tanvi rajiv Aggarwal Department of Mathematics Shaheed Rajguru College of Applied Sciences for WomenUniversity of DelhiNew Delhi-110096India Department of Mathematics Deshbandhu CollegeUniversity of DelhiNew Delhi-110019India

In this paper,a nonlinear population model for HIV-TB co-infection has been *** model is incorporated with the effect of early and late initiation of HIV treatment in co-infectives already on TB treatment,on the occurrence of Immune Reconstitution Inflammatory syndrome(IRIS).A 15-dimensional(15D)mathematical model has been developed in this *** begin with considering constant treatment rates and thereafter,proceed to time-dependent treatment rates for co-infectives as control *** basic reproduction number,a threshold quantity,corresponding to each HIV and TB sub-model has been computed in case of constant *** constant values of control parameters,mathematical analysis shows the existence and local stability of the disease-free equilibrium point and the endemic equilibrium point for the *** with time-dependent parameters,an optimal control problem is introduced and solved using Pontryagin’s maximum principle with an objective to minimize the number of infectives and disease induced deaths along with the cost of *** simulations are performed to examine the effect of reproduction numbers on control profiles and to identify,the ideal combination of treatment strategies which provides minimum burden on a *** results imply that if both HIV and TB are endemic in the population,then in order to bring in minimum burden from the co-infection,optimal control efforts must be enforced rather than constant treatment rate.

关键词： HIV tuberculosis co-infection IRIS stability optimal control

Liquid-liquid extraction of phosphorus from sulfuric acid solution using benzyl dimethyl amine

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International Journal of Minerals,Metallurgy and Materials 2021年第3期28卷 367-372页

作者： Sadia Ilyas rajiv Ranjan Srivastava Hyunjung Kim Department of Mineral Resources and Energy Engineering Jeonbuk National UniversityJeonjuJeonbuk 54896Republic of Korea Center for Advanced Chemistry Institute of Research and DevelopmentDuy Tan UniversityDa Nang 550000Vietnam Faculty of Natural Sciences Duy Tan UniversityDa Nang 550000Vietnam

This study addresses the liquid-liquid extraction behavior of phosphorus from a sulfuric acid solution using benzyl dimethyl amine(BDMA)in *** extraction equilibria investigated with varied BDMA concentrations could reveal the formation of 3[BDMA]·[H_(3)PO_(4)]^(-)complex in the organic *** thermodynamic properties determined at various temperatures indicated that the process was exothermic with a calculated enthalpy(△H^(Θ))of−24.0 kJ·mol^(−1).The organic-to-aqueous phase(O/A)volume ratio was varied to elucidate the quantitative extraction of *** McCabe-Thiele diagram plotted for the extraction isotherm was validated for the requirement of three counter-current stages in the extraction at an O/A volume ratio of 2.0/*** back-extraction of phosphorus from the loaded organic phase was quantitatively achieved by contacting 4.0 mol·L−1 H2SO4 solution in three stages of counter-current contact at an O/A volume ratio of 3/*** study can be applied to remove phosphorus from the sulfuric acid leach solutions of monazite processing,and many other solutions.

关键词： solvent extraction phosphorus benzyl dimethyl amine(BDMA) sulfuric acid solution McCabe-Thiele diagram

Proactive Connection Recovery Strategy with Recovery Time Constraint for Survivable Elastic Optical Networks

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China Communications 2021年第9期18卷 236-248页

作者： Dinesh Kumar rajiv Kumar Neeru Sharma Department of Electronics&Communication Engineering Jaypee University of Information Technology WaknaghatSolan(HP)India

This paper presents a halfway signaling exchange shared path protection(HSE-SPP)on the backup route for a fast connection recovery *** the proposed HSE-SPP,a pre-assigned intermediate node on the backup route is chosen for signaling *** connection fails,source and destination nodes simultaneously generate backup connection setup messages to the pre-assigned intermediate node on the reserved backup *** the intermediate node,signaling process occurs,and acknowledgment is generated for data transmission to the respective end ***,connection recovery time by applying HSE-SPP becomes very *** are performed for network parameters and results are verified with existing *** average recovery time(RT),bandwidth blocking probability(BBP),bandwidth provisioning ratio(BPR),and resource overbuild(RO)ratio of HSE-SPP for ARPANET is 13.54 ms,0.18,3.02,0.55,and for dedicated path protection(DPP)are 13.20 ms,0.56,6.30,3.75 and for shared path protection(SPP)22.19 ms,0.22,3.23,0.70 ***,average RT,BBP,BPR and RO of HSE-SPP for COST239 are8.33 ms,0.04,1.64,0.26,and for DPP 4.23,0.47,3.50,2.04,and for SPP 11.81,0.08,1.66,0.27 ***,results of the proposed strategy are better in terms of RT,BBP,BPR,and RO ratio.

关键词： routing and spectrum assignment halfway signaling exchange-shared path protection(HSE-SPP) dedicated path protection bandwidth blocking probability(BBP)

Assessing the effects of different dielectrics onenvironmentally conscious powder-mixed EDM of difficult-to-machine material （WC-Co）

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Frontiers of Mechanical Engineering 2016年第4期11卷 374-387页

作者： Jagdeep SINGH rajiv Kumar SHARMA Department of Mechanical Engineering National Institute of Technol-ogy Hamirpur Himachal Pradesh-177005 India

Electrical discharge machining (EDM) is a well-known nontraditional manufacturing process to machine the difficult-to-machine (DTM) materials which have unique hardness properties. Researchers have successfully performed hybridization to improve this process by incorporating powders into the EDM process known as powder-mixed EDM process. This process drastically improves process efficiency by increasing material removal rate, micro-hardness, as well as reducing the tool wear rate and surface roughness. EDM also has some input parameters, including pulse-on time, dielectric levels and its type, current setting, flushing pressure, and so on, which have a significant effect on EDM performance. However, despite their positive influence, investigating the effects of these parameters on environmental conditions is necessary. Most studies demonstrate the use of kerosene oil as dielectric fluid. Nevertheless, in this work, the authors highlight the findings with respect to three different dielectric fluids, including kerosene oil, EDM oil, and distilled water using one-variable-at-a-time approach for machining as well as environmental aspects. The hazard and operability analysis is employed to identify the inherent safety factors associated with powder-mixed EDM of WC-Co.

关键词： WC hazard and operability analysis (HAZOP) discharging aerosol concentration dielectrics powders

Effect of friction stir processed microstructure on tensile properties of an Al-Zn-Mg-Sc alloy upon subsequent aging heat treatment

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Journal of Materials Science & Technology 2018年第1期34卷 214-218页

作者： Indrajit Charit rajiv S.Mishra Department of Chemical & Materials Engineering University of Idaho Moscow ID 83844 USA Department of Materials Science & Engineering University of North Texas Denton TX 76203 USA

An as-cast Al-Zn-Mg-Sc alloy was friction stir processed varying tool related parameters, yielding microstructures with different grain sizes （0.68, 1.8 and 5.5 μm）. Significant increases in room temperature ductility were obtained in these materials with reasonable enhancement in strength. It is demonstrated that the type of microstructure produced by friction stir processing （FSP） has a significant influence on the choice of post-FSP heat treatment design for achieving improved tensile properties. It is also found that the ultrafine grained FSP material could not achieve the desired high strength during the post-FSP heat treatment without grain coarsening, whereas the micro-grained FSP materials could reach such strength levels （〉560 MPa） under conventional age hardening heat treatment conditions.

关键词： Friction stir processing Microstructure Tensile properties Heat treatment