Structural and magnetic characterization of two tetranuclear Cu(II) complexes with closed‐cubane‐like core framework

Two novel tetranuclear Cu(II) complexes [Cu4(L1)4]·3(H2O) (1) and [Cu4(H2L2)4(H2O)4] (2) ( H2L1 = (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol; H4L2 = 2-((2-hydroxy-3-methoxybenzylidene)amino)-2-hydroxymethylpropane-1,3-diol) were synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligands. Both complexes crystallize in the tetragonal system with space group I 41/a and form tetranuclear species with closed-cubane like core framework. Both the complexes possess a S4 axis but of different stereochemistry due to the different arrangement of the ligands about the copper ions. Variable temperature magnetic susceptibility measurements indicate an overall weak antiferromagnetic exchange coupling in 1, while ferromagnetic exchange coupling in 2. In agreement with their closed-cubane structure, the magnetic behavior of the two complexes have been studied by employing the isotropic spin Hamiltonian of type H = J1 (S1S3 + S1S4 + S2S3 + S2S4) - J2 (S1S2 + S3S4) (J1 describes the magnetic exchange coupling between the four Cu(II) pairs with short Cu···Cu distances, while J2 characterizes the magnetic exchange coupling between the remaining two intermetallic pairs with long distances). The PHI program was used to study their magnetic behavior. A good agreement between the experimental and fitted curves was found with the following parameters: g = 2.14, J1 = -20.3 cm-1 and J2 = 0 cm-1 for 1 and g = 2.10, J1 = 101.1 cm-1 and J2 = -51.5 cm-1 for 2

The Impact, Emerging Needs, and New Research Questions Arising from 12 Years of the Center for the Study of Complex Malaria in India

The Center for the Study of Complex Malaria in India (CSCMi) was launched in 2010 with the overall goal of addressing major gaps in our understanding of "complex malaria" in India through projects on the epidemiology, transmission, and pathogenesis of the disease. The Center was mandated to adopt an integrated approach to malaria research, including building capacity, developing infrastructure, and nurturing future malaria leaders while conducting relevant and impactful studies to assist India as it moves from control to elimination. Here, we will outline some of the interactions and impacts the Center has had with malaria policy and control counterparts in India, as well as describe emerging needs and new research questions that have become apparent over the past 12 years

Genetics of chloroquine-resistant malaria: a haplotypic view

The development and rapid spread of chloroquine resistance (CQR) in Plasmodium falciparum have triggered the identification of several genetic target(s) in the P. falciparum genome. In particular, mutations in the Pfcrt gene, specifically, K76T and mutations in three other amino acids in the region adjoining K76 (residues 72, 74, 75 and 76), are considered to be highly related to CQR. These various mutations form several different haplotypes and Pfcrt gene polymorphisms and the global distribution of the different CQR- Pfcrt haplotypes in endemic and non-endemic regions of P. falciparum malaria have been the subject of extensive study. Despite the fact that the Pfcrt gene is considered to be the primary CQR gene in P. falciparum , several studies have suggested that this may not be the case. Furthermore, there is a poor correlation between the evolutionary implications of the Pfcrt haplotypes and the inferred migration of CQR P. falciparum based on CQR epidemiological surveillance data. The present paper aims to clarify the existing knowledge on the genetic basis of the different CQR- Pfcrt haplotypes that are prevalent in worldwide populations based on the published literature and to analyse the data to generate hypotheses on the genetics and evolution of CQR malaria

DNA sequence variation and determination of the putative PvCSP gene as potential vaccine target for Plasmodium vivax malaria in India

Evolutionary genetic studies in genomes offer excellent opportunities to infer population structure and demographic history of species populations. However, such kinds of studies are very limited in malaria. Malaria is highly endemic in India and both of the causative agents of malaria, Plasmodium vivax and Plasmodium falciparum occur in almost equal proportion. The widespread distribution of P. vivax is attributing to socio-economic loss, and thereby increasing the public health concern. Therefore, it is important to understand the genetic features of P. vivax population in India. Comparative genomics of P. falciparum and P. vivax has revealed several syntenic chromosomal segments. One such 200 kb segment has been utilized to design several small DNA fragments from non-coding regions, and tested for ‘putatively neutral’ marker for inference of population structure and demography of P. vivax. Utilizing 126 P. vivax isolates collected from 10 different widespread geographic locations in India, it was found that two neutral DNA fragments (P10 and P17) showed fairly less nucleotide diversity in all the population samples of P. vivax. A sudden drop in diversity in putatively neutral genetic fragments indicates the role of positive natural selection under the hitchhiking model of molecular evolution. Evolutionary genetic studies in the regions surrounding P10 and P17 with functional validation might provide meaningful insights and help identify targets in P. vivax in India. The study can further extended to P.falciparum as it is syntenic to P.vivax. It was found that the neutral fragment P17 is flanked by putative circumsporozoite protein (PvCSP) gene. Since, CSP is a major surface protein of the infective stage of malaria parasite; it is believed that the PvCSP gene might be under a certain kind of selective pressure. The objective of this study is to obtain new DNA sequence information of the putative PvCSP gene in isolates from India and compare it with the estimated diversity of the non-coding DNA fragments located in-and around this gene for inference of natural selection. Effectiveness of putative PvCSP gene as a suitable vaccine candidate on the basis of genetic diversity in parasite populations can be evaluated

Inferring the Population Structure and Demography of Drosophila ananassae From Multilocus Data

Inferring the origin, population structure, and demographic history of a species is a major objective of population genetics. Although many organisms have been analyzed, the genetic structures of subdivided populations are not well understood. Here we analyze Drosophila ananassae, a highly substructured, cosmopolitan, and human-commensal species distributed in the tropical, subtropical, and mildly temperate regions of the world. We adopt a multilocus approach (with 10 neutral loci) using 16 population samples covering almost the entire species range (Asia, Australia, and America). Analyzed with our recently developed Bayesian method, 5 populations in Southeast Asia are found to be central, while the other 11 are peripheral. These 5 central populations were sampled from localities that belonged to a single landmass (“Sundaland”) during the late Pleistocene (∼18,000 years ago), when sea level was ∼120 m below the present level. The inferred migration routes of D. ananassae out of Sundaland seem to parallel those of humans in this region. Strong evidence for a population size expansion is seen particularly in the ancestral populations