Plasmodium Falciparum Protein Research Articles

Understanding the Development of Compensatory Pathways in a Mutant Malaria Parasite Harbouring Hypomorphic Allele of Plant-Like Kinases.

One of the mechanisms for subverting the effect of drugs bythe malaria parasite is through rewiring of its transcriptome. The effect is more pronounced for target genes belonging to the multigene family. Plasmodium falciparum protein kinases belonging to the CDPK family are essential for blood stage development. As such, CDPKs are considered good targets for the development of anti-malarial compounds. The chemical genetics approach has been historically used to elucidate the function of protein kinases in higher eukaryotes. It requires the substitution of gatekeeper residue for another amino acid with a different side chain through genetic manipulation. Amino acid substitution at the gatekeeper position modulates the activity of a protein kinase and changes its susceptibility to a specific class of compounds known as bumped kinase inhibitors (BKIs) that help in the functional identification of the target gene. Here, we have exploited the chemical genetics approach to understand compensatory mechanisms evolved by a mutant parasite harboring a hypomorphic allele of cdpk1. Overall, our approach helps in identifying compensatory pathways that may be simultaneously targeted to prevent the development of drug resistance against individual kinases.

Plasmodium falciparum protein phosphatase PP7 is required for early ring-stage development.

Plasmodium falciparum causes malaria and is responsible for more than 600,000 deaths each year. Although effective drugs are available to treat disease, the spread of drug-resistant parasites endangers their future efficacy. It is hoped that a better understanding of the biology of malaria parasites will help us to discover new drugs to tackle the resistance problem. Our work is focused on the cell signaling mechanisms that control the development of the parasite throughout its complex life cycle. All signal transduction pathways are ultimately regulated by reversible protein phosphorylation by protein kinase and protein phosphatase enzymes. In this study, we investigate the function of calcium-dependent protein phosphatase PP7 and show that it is essential for the development of ring-stage parasites following the invasion of human erythrocytes. Our results contribute to the understanding of the erythrocytic stages of the parasite life cycle that cause malaria pathology.

Phytochemicals of Swertia chirayita Roxb. ex Fleming against malarial dihydroorotate dehydrogenase: an in silico study

The global economic burden of malaria is rising and lack of effective drugs against it have imposed an insurmountable challenge in designing it that is both affordable and resistanceless. The plants with ethnobotanical values are relatively safer and its use is a viable option as therapeutics for various demographic locations. In this regard, the chemical components of a plant, Swertia chirayita Roxb. ex Fleming (traditionally used as an antimalarial agent) were explored by multiple computational tools against dihydroorotate dehydrogenase (DHODH) protein of Plasmodium falciparum (PDB ID: 6GJG), a causative agent of the disease. The docking scores were calculated to be − 10.220, − 10.131, − 10.071, − 10.024, and − 9.905 kcal/mol for the top five molecules (decussatin, swerchirin, 1-hydroxy-3,5,8-trimethoxyxanthen-9-one, swertinin, and chiratol), respectively with the native ligand possessing a higher value of − 9.873 kcal/mol. The adducts were geometrically and thermodynamically stable as revealed by several parameters extracted from 200 ns molecular dynamics simulations (MDS) and verified by a single run of 600 ns. The smooth RMSD profiles from a cumulative MDS of 2.0 μs, pointed towards a sturdy nature of the receptor geometry with limited translational or rotational motion of the ligands. The involvement of LEU11, CYS14, LEU15, CYS23, PHE27, ILE102, ARG104, TYR337, LEU340, and VAL341 amino acid residues with mainly hydrophobic interactions at the orthosteric site were observed for most of the adducts. The binding free energy changes (up to − 30.18 ± 4.38 kcal/mol) hinted at the feasibility and sustained thermodynamical spontaneity of the forward reaction of the complex formation. The hit molecules could possibly disrupt or inhibit the normal functioning of the DHODH receptor leading to the likely prevention and cure of the disease and are recommended for experimental trials.

A screen for Plasmodium falciparum sporozoite surface protein binding to human hepatocyte surface receptors identifies novel host–pathogen interactions

BackgroundSporozoite invasion of hepatocytes is an essential step in the Plasmodium life-cycle and has similarities, at the cellular level, to merozoite invasion of erythrocytes. In the case of the Plasmodium blood-stage, efforts to identify host–pathogen protein–protein interactions have yielded important insights including vaccine candidates. In the case of sporozoite-hepatocyte invasion, the host–pathogen protein–protein interactions involved are poorly understood.MethodsTo gain a better understanding of the protein–protein interaction between the sporozoite ligands and host receptors, a systematic screen was performed. The previous Plasmodium falciparum and human surface protein ectodomain libraries were substantially extended, resulting in the creation of new libraries comprising 88 P. falciparum sporozoite protein coding sequences and 182 sequences encoding human hepatocyte surface proteins. Having expressed recombinant proteins from these sequences, a plate-based assay was used, capable of detecting low affinity interactions between recombinant proteins, modified for enhanced throughput, to screen the proteins for interactions. The novel interactions identified in the screen were characterized biochemically, and their essential role in parasite invasion was further elucidated using antibodies and genetically manipulated Plasmodium parasites.ResultsA total of 7540 sporozoite-hepatocyte protein pairs were tested under conditions capable of detecting interactions of at least 1.2 µM KD. An interaction between the human fibroblast growth factor receptor 4 (FGFR4) and the P. falciparum protein Pf34 is identified and reported here, characterizing its affinity and demonstrating the blockade of the interaction by reagents, including a monoclonal antibody. Furthermore, further interactions between Pf34 and a second P. falciparum rhoptry neck protein, PfRON6, and between human low-density lipoprotein receptor (LDLR) and the P. falciparum protein PIESP15 are identified.Conditional genetic deletion confirmed the essentiality of PfRON6 in the blood-stage, consistent with the important role of this protein in parasite lifecycle. Pf34 was refractory to attempted genetic modification. Antibodies to Pf34 abrogated the interaction and had a modest effect upon sporozoite invasion into primary human hepatocytes.ConclusionPf34 and PfRON6 may be members of a functionally important invasion complex which could be a target for future interventions. The modified interaction screening assay, protein expression libraries and P. falciparum mutant parasites reported here may be a useful tool for protein interaction discovery and antigen candidate screening which could be of wider value to the scientific community.

Identification and characterization of nuclear localization signals in the circumsporozoite protein of Plasmodium falciparum.

Secretory proteins of Plasmodium exhibit differential spatial and functional activity within the host cell nucleus. However, the nuclear localization signals (NLSs) for these proteins remain largely uncharacterized. In this study, we have identified and characterized two NLSs in the circumsporozoite protein of Plasmodium falciparum (Pf-CSP). Both NLSs in the Pf-CSP contain clusters of lysine and arginine residues essential for specific interactions with the conserved tryptophan and asparagine residues of importin-α, facilitating nuclear translocation of Pf-CSP. While the two NLSs of Pf-CSP function independently and are both crucial for nuclear localization, a single NLS of Pf-CSP leads to weak nuclear localization. These findings shed light on the mechanism of nuclear penetrability of secretory proteins of Plasmodium proteins.

Proteome-Wide Identification of RNA-dependent proteins and an emerging role for RNAs in Plasmodium falciparum protein complexes

Ribonucleoprotein complexes are composed of RNA, RNA-dependent proteins (RDPs) and RNA-binding proteins (RBPs), and play fundamental roles in RNA regulation. However, in the human malaria parasite, Plasmodium falciparum, identification and characterization of these proteins are particularly limited. In this study, we use an unbiased proteome-wide approach, called R-DeeP, a method based on sucrose density gradient ultracentrifugation, to identify RDPs. Quantitative analysis by mass spectrometry identifies 898 RDPs, including 545 proteins not yet associated with RNA. Results are further validated using a combination of computational and molecular approaches. Overall, this method provides the first snapshot of the Plasmodium protein-protein interaction network in the presence and absence of RNA. R-DeeP also helps to reconstruct Plasmodium multiprotein complexes based on co-segregation and deciphers their RNA-dependence. One RDP candidate, PF3D7_0823200, is functionally characterized and validated as a true RBP. Using enhanced crosslinking and immunoprecipitation followed by high-throughput sequencing (eCLIP-seq), we demonstrate that this protein interacts with various Plasmodium non-coding transcripts, including the var genes and ap2 transcription factors.

N-Substituted Phenylhydrazones Kill the Ring Stage of Plasmodium falciparum.

Antimalarial resistance has hampered the effective treatment of malaria, a parasitic disease caused by Plasmodium species. As part of our campaign on phenotypic screening of phenylhydrazones, a library of six phenylhydrazones was reconstructed and evaluated for their in vitro antimalarial and in silico receptor binding and pharmacokinetic properties. The structures of the phenylhydrazone hybrids were largely confirmed using nuclear magnetic resonance techniques. We identified two compounds which exhibited significant antimalarial potential against the ring stage (trophozoite) of 3D7 chloroquine-sensitive (CS) strain and DD2 chloroquine-resistant (CR) strains of Plasmodium falciparum with monosubstituted analogs bearing meta or para electron-donating groups showing significant activity in the single-digit micromolar range. Structure activity relationship is presented showing that electron-donating groups on the substituent hydrophobic pharmacophore are required for antimalarial activity. Compounds PHN6 and PHN3 were found to be the most potent with pIC50s (calculated form in vitro IC50s) of 5.37 and 5.18 against 3D7 CS and DD2 CR strains, respectively. Our selected ligands (PHN3 and PHN6) performed better when compared to chloroquine regarding binding affinity and molecular stability with the regulatory proteins of Plasmodium falciparum, hence predicted to be largely responsible for their in vitro activity. Pharmacokinetic prediction demonstrated that the phenylhydrazones may not cross the blood-brain barrier and are not P-glycoprotein (P-gp) substrates, a good absorption of 62% to 69%, and classified as a category IV compound based on toxicity grading.

Betulinic and ursolic acids from Nauclea latifolia roots mediate their antimalarial activities through docking with PfEMP-1 and PfPKG proteins

BackgroundChemotherapies target the PfEMP-1 and PfPKG proteins in Plasmodium falciparum, the parasite that causes malaria, in an effort to prevent the disease’s high fatality rate. This work identified the phytochemical components of Nauclea latifolia roots and docked the chemical compounds against target proteins, and examined the in vivo antiplasmodial effect of the roots on Plasmodium berghei-infected mice.MethodsStandard protocols were followed for the collection of the plant’s roots, cleaning, and drying of the roots, extraction and fraction preparation, assessment of the in vivo antiplasmodial activity, retrieval of the PfEMP-1 and PfPKG proteins, GCMS, ADME, and docking studies, chromatographic techniques were employed to separate the residual fraction’s components, and the Swis-ADME program made it possible to estimate the drug’s likeness and pharmacokinetic properties. The Auto Dock Vina 4.2 tool was utilized for molecular docking analysis.ResultsThe residual fraction showed the best therapeutic response when compared favorably to amodiaquine (80.5%) and artesunate (85.1%). It also considerably reduced the number of parasites, with the % growth inhibition of the parasite at 42.8% (D2) and 83.4% (D5). Following purification, 25 compounds were isolated and characterized with GCMS. Based on their low molecular weights, non-permeation of the blood–brain barrier, non-inhibition of metabolizing enzymes, and non-violation of Lipinski’s criteria, betulinic and ursolic acids were superior to chloroquine as the best phytochemicals. Hence, they are lead compounds.ConclusionIn addition to identifying the bioactive compounds, ADME, and docking data of the lead compounds as candidates for rational drug design processes as observed against Plasmodium falciparum target proteins (PfEMP-1 and PfPKG), which are implicated in the pathogenesis of malaria, the study has validated that the residual fraction of N. latifolia roots has the best antiplasmodial therapeutic index.

Inhibitors of Protein Targets of Plasmodium falciparum

The World Health Organization documented 247 million reported malaria cases worldwide resulting in 619,000 fatalities in 2021. More than 70% of these deaths are attributed to Children under five years of age and sub-Saharan Africa is the region in which the highest number of deaths occur. The Plasmodium falciparum parasite is the deadliest form of malaria, and treating falciparum infection is becoming more challenging due to the emergence of drug-resistant parasites, causing a decrease in the efficiency of antimalarial medications. Artemisinin combination therapy is now considered the gold standard for malaria treatment; however, this method is at risk due to parasites exhibiting delayed clearance to artemisinin and resistance to partner drugs such as lumefantrine, amodiaquine, mefloquine, piperaquine, and sulfadoxine/pyrimethamine. This review assessed drug targets in Plasmodium falciparum for the development of novel antimalarials. Over Eighty-five papers on malaria, Plasmodium falciparum protein targets, and protein inhibitors were gathered from Google Scholar, ProQuest, PubMed, and Science Direct, between 2012 and 2023. Only articles with comparable keywords on malaria drug targets concentrating on enzyme proteins, carrier molecules present in Plasmodium falciparum, and their inhibitors were retrieved for review, while articles within that range that did not provide definite data were excluded. Most recently, inhibitors of dihydroorotate dehydrogenase (DHODH), artefenomel (OZ439), and ferroquine have been reported and are being explored in combination with other partner medications to work against different stages of plasmodium parasite. In identifying target proteins for drug development, essentiality and vulnerability throughout the life cycle of the parasite, its druggability, and the availability of target-based assays are critical factors. The use of modern proteomics and cellular proteins from database search which assists in parasite proliferation delivers optimal information on the new generation of lead compounds. In addition, advances in in silico methods enable the identification of protein targets for drug development.

Comparative analysis of codon usage patterns of Plasmodium helical interspersed subtelomeric (PHIST) proteins.

Plasmodium falciparum is a protozoan parasite that causes the most severe form of malaria in humans worldwide, which is predominantly found in sub-Saharan Africa, where it is responsible for the majority of malaria-related deaths. Plasmodium helical interspersed subtelomeric (PHIST) proteins are a family of proteins, with a conserved PHIST domain, which are typically located at the subtelomeric regions of the Plasmodium falciparum chromosomes and play crucial roles in the interaction between the parasite and its human host, such as cytoadherence, immune evasion, and host cell remodeling. However, the specific utilization of synonymous codons by PHIST proteins in Plasmodium falciparum is still unknown. Codon usage bias (CUB) refers to the unequal usage of synonymous codons during translation, resulting in over- or underrepresentation of certain nucleotide patterns. This imbalance in CUB can impact various cellular processes, including protein expression levels and genetic variation. To investigate this, the CUB of 88 PHIST protein coding sequences (CDSs) from 5 subgroups were analyzed in this study. The results showed that both codon base composition and relative synonymous codon usage (RSCU) analysis identified a higher occurrence of AT-ended codons (AGA and UUA) in PHIST proteins of Plasmodium falciparum. The average effective number of codons (ENC) for these PHIST proteins was 36.69, indicating a weak codon preference among them, as it was greater than 35. Additionally, the correlation analysis among codon base composition (GC1, GC2, GC3, GCs), codon adaptation index (CAI), codon bias index (CBI), frequency of optimal codons (FOP), ENC, general average hydropathicity (GRAVY), aromaticity (AROMO), length of synonymous codons (L_sym), and length of amino acids (L_aa) revealed the influence of base composition and codon usage indices on codon usage bias, with GC1 having a significant impact in this study. Furthermore, the neutrality plot analysis, PR2-bias plot analysis, and ENC-GC3 plot analysis provided additional evidence that natural selection plays a crucial role in determining codon bias in PHIST proteins. In conclusion, this study has enhanced our understanding of the characteristics of codon usage and genetic evolution in PHIST proteins, thereby providing data foundation for further research on antimalarial drugs or vaccines.

Computational Molecular Docking Studies for Antimalarial Drug Discovery Against Plasmodium falciparum

Malaria, a deadly disease caused by the Plasmodium falciparum parasite, poses a global health crisis with limited treatment options due to drug resistance. In the quest for new antimalarial drugs, computational molecular docking has emerged as a pivotal approach. This study delves into the application of computational docking techniques to identify potential drug candidates targeting critical proteins within the parasite. Leveraging genetic and structural data, we scrutinize key Plasmodium falciparum proteins involved in essential biological processes. The evaluation of various computational methodologies, including molecular dynamics simulations and scoring functions, aids in the identification of promising compounds. Additionally, we highlight recent advances in machine learning and artificial intelligence for more efficient virtual screening. The results of these studies provide a promising pool of candidate compounds, accelerating the development of novel antimalarial drugs to combat this persistent global health threat. Keywords: Computational Molecular Docking, Plasmodium falciparum, Molecular Dynamics, Protein- Ligand Interactions, Protein Structure.

Potentials of Terpenoids as Inhibitors of Multiple Plasmodium falciparum Protein Drug Targets.

The resistance of parasite to readily affordable antimalarial drugs, the high cost of currently potent drugs, and the resistance of vector mosquitoes to insecticides threaten the possibility of malaria eradication in malaria endemic areas. Due to the fact that quinine and artemisinin were isolated from plants sources, researchers have been encouraged to search for new antimalarials from medicinal plants. This is especially the case in Africa where a large percentage of the population depends on medicinal plant to treat malaria and other ailments. In this study, we evaluated previously characterized Plasmodium-cidal compounds obtained from the African flora to identify their likely biochemical targets, for an insight into their possible antimalarial chemotherapy. Molecular docking study was first conducted, after which remarkable compounds were submitted for molecular dynamic (MD) simulations studies. From a total of 38 Plasmodium-cidal compounds docked with confirmed Plasmodium falciparum protein drug targets [plasmepsin II (PMII), histo-aspartic protein (HAP) and falcipain-2 (FP)], two pentacyclic triterpene, cucurbitacin B and 3 beta-O-acetyl oleanolic acid showed high binding affinity relative to artesunate. This implies their capacity to inhibit the three selected P. falciparum target proteins, and consequently, antimalarial potential. From the MD simulations studies and binding free energy outcomes, results confirmed that the two compounds are stable in complex with the selected antimalarial targets; they also showed excellent binding affinities during the 100 ns simulation. These results showed that cucurbitacin B and 3 beta-O-acetyl oleanolic acid are potent antimalarials and should be considered for further studies.

A genomic platform for surveillance and antigen discovery in Plasmodium spp. using long-read amplicon sequencing

Many vaccine candidate proteins in the malaria parasite Plasmodium falciparum are under strong immunological pressure and confer antigenic diversity. We present a sequencing and data analysis platform for the genomic surveillance of the insertion or deletion (indel)-rich antigens merozoite surface protein 1 (MSP1), MSP2, glutamate-rich protein (GLURP), and CSP from P.falciparum using long-read circular consensus sequencing (CCS) in multiclonal malaria isolates. Our platform uses 40 PCR primers per gene to asymmetrically barcode and identify multiclonal infections in pools of up to 384 samples. With msp2, we validated the method using 235 mock infections combining 10 synthetic variants at different concentrations and infection complexities. We applied this strategy to P.falciparum isolates from a longitudinal cohort in Tanzania. Finally, we constructed an analysis pipeline that streamlines the processing and interpretation of epidemiological and antigenic diversity data from demultiplexed FASTQ files. This platform can be easily adapted to other polymorphic antigens of interest in Plasmodium or any other human pathogen.

Ex vivo and In vitro antiplasmodial activities of approved drugs predicted to have antimalarial activities using chemogenomics and drug repositioning approach

High malaria mortality coupled with increased emergence of resistant multi-drug resistant strains of Plasmodium parasite, warrants the development of new and effective antimalarial drugs. However, drug design and discovery are costly and time-consuming with many active antimalarial compounds failing to get approved due to safety reasons. To address these challenges, the current study aimed at testing the antiplasmodial activities of approved drugs that were predicted using a target-similarity approach. This approach is based on the fact that if an approved drug used to treat another disease targets a protein similar to Plasmodium falciparum protein, then the drug will have a comparable effect on P. falciparum. In a previous study, in vitro antiplasmodial activities of 10 approved drugs was reported of the total 28 approved drugs. In this study, six out of 18 drugs that were previously not tested, namely epirubicin, irinotecan, venlafaxine, palbociclib, pelitinib, and PD153035 were tested for antiplasmodial activity. The drug susceptibility in vitro assays against five P. falciparum reference strains (D6, 3D7, W2, DD2, and F32 ART) and ex vivo assays against fresh clinical isolates were done using the malaria SYBR Green I assay. Standard antimalarial drugs were included as controls. Epirubicin and irinotecan showed excellent antiplasmodial ex vivo activity against field isolates with mean IC50 values of 0.044 ± 0.033 μM and 0.085 ± 0.055 μM, respectively. Similar activity was observed against W2 strain where epirubicin had an IC50 value of 0.004 ± 0.0009 μM, palbociclib 0.056 ± 0.006 μM, and pelinitib 0.057 ± 0.013 μM. For the DD2 strain, epirubicin, irinotecan and PD 153035 displayed potent antiplasmodial activity (IC50 < 1 μM). Epirubicin and irinotecan showed potent antiplasmodial activities (IC50 < 1 μM) against DD2, D6, 3D7, and F32 ART strains and field isolates. This shows the potential use of these drugs as antimalarials. All the tested drugs showed antiplasmodial activities with IC50 values below 20 μM, which suggests that our target similarity-based strategy is successful at predicting antiplasmodial activity of compounds thereby circumventing challenges in antimalarial drug discovery.

Antimalarial Activities of a Therapeutic Combination of Azadirachta indica, Mangifera indica and Morinda lucida Leaves: A Molecular View of its Activity on Plasmodium falciparum Proteins.

The search for new antimalarial drugs remains elusive prompting research into antimalarial combinations from medicinal plants due to their cheapness, efficacy and availability. Azadirachta indica (AI), Morinda lucida (ML) and Mangifera indica (MI) have all been reported as potent antimalarial plants. This study evaluated the efficacy of an antimalarial combination therapeutics prepared from leaves of AI, ML and MI using in vitro, in vivo and molecular methods. Refined extracts of the plants combination was made by partitioning the aqueous extract of plants combinations (AI + MI, AI + ML, MI + ML, AI + MI + ML) using methanol and ethyl acetate consecutively. The resulting ethyl acetate partitioned fraction was evaluated for its antimalarial activity. Molecular docking and molecular dynamics simulation were employed to determine the possible mechanism of action of the constituent of the most active combination against four important P. falciparum proteins. The result revealed that the refined extract from combinations AI + ML and MI + ML at 16mg/kg bodyweight have the highest chemo-suppressive effect of 90.7% and 91.0% respectively compared to chloroquine's 100% at 10mg/kg. Also, refined extract from MI + ML combination improved PCV levels significantly (p < 0.05) compared to controls. Molecular docking revealed oleanolic acid and ursolic acid as multiple inhibitors of plasmepsin II, hiso-aspartic protease, falcipain-2 and P. falciparum Eonyl acyl-carrier protein reductase with relative stability during 100ns of simulation. The study unveiled the potentials of ML and MI as good candidates for antimalarial combination therapy and further established their use together as revealed in folklore medicine.

Synthesis and activity of β-carboline antimalarials targeting the Plasmodium falciparum heat shock 90 protein

A collection of β-carbolines based on the natural product harmine, a compound known to target the heat shock 90 protein of Plasmodium falciparum, was synthesized and tested for antimalarial activity and potential toxicity. Several of these novel compounds display promising bioactivity, providing a new potential therapeutic with a mode of action that differs versus any currently available clinical treatment.

PlasmoFAB: a benchmark to foster machine learning for Plasmodium falciparum protein antigen candidate prediction.

Machine learning methods can be used to support scientific discovery in healthcare-related research fields. However, these methods can only be reliably used if they can be trained on high-quality and curated datasets. Currently, no such dataset for the exploration of Plasmodium falciparum protein antigen candidates exists. The parasite P.falciparum causes the infectious disease malaria. Thus, identifying potential antigens is of utmost importance for the development of antimalarial drugs and vaccines. Since exploring antigen candidates experimentally is an expensive and time-consuming process, applying machine learning methods to support this process has the potential to accelerate the development of drugs and vaccines, which are needed for fighting and controlling malaria. We developed PlasmoFAB, a curated benchmark that can be used to train machine learning methods for the exploration of P.falciparum protein antigen candidates. We combined an extensive literature search with domain expertise to create high-quality labels for P.falciparum specific proteins that distinguish between antigen candidates and intracellular proteins. Additionally, we used our benchmark to compare different well-known prediction models and available protein localization prediction services on the task of identifying protein antigen candidates. We show that available general-purpose services are unable to provide sufficient performance on identifying protein antigen candidates and are outperformed by our models that were trained on this tailored data. PlasmoFAB is publicly available on Zenodo with DOI 10.5281/zenodo.7433087. Furthermore, all scripts that were used in the creation of PlasmoFAB and the training and evaluation of machine learning models are open source and publicly available on GitHub here: https://github.com/msmdev/PlasmoFAB.

Expression and copper binding studies of a Plasmodium falciparum protein with Cox19 copper binding motifs

Copper can exist in an oxidized and a reduced form, which enables the metal to play essential roles as a catalytic co-factor in redox reactions in many organisms. Copper confers redox activity to the terminal electron transport chain cytochrome c oxidase protein. Cytochrome c oxidase in yeast obtains copper for the CuB site in the Cox1 subunit from Cox11 in association with Cox19. When copper is chelated in growth medium, Plasmodium falciparum parasite development in infected red blood cells is inhibited and excess copper is toxic for the parasite. The gene of a 26 kDa Plasmodium falciparum PfCox19 protein with two Cx9C Cox19 copper binding motifs, was cloned and expressed as a 66 kDa fusion protein with maltose binding protein and affinity purified (rMBP-PfCox19). rMBP-PfCox19 bound copper measured by: a bicinchoninic acid release assay; an in vivo bacterial host growth inhibition assay; ascorbate oxidation inhibition and differential scanning fluorimetry. The native protein was detected by antibodies raised against rMBP-PfCox19. PfCox19 binds copper and is predicted to associate with PfCox11 in the insertion of copper into the CuB site of Plasmodium cytochrome c oxidase. Characterisation of the proteins involved in Plasmodium spp. copper metabolism will help us understand the role of cytochrome c oxidase and this essential metal in Plasmodium homeostasis.

Highly selective Schiff base functionalized silatrane based receptor as Sn(II) ion chemosensor: Synthesis, photophysical, DFT and docking studies

This article illustrates the successful formation of Schiff base of 3-methyl-2-thiophenecarboxyaldehyde based silanes and their corresponding silatranes and silocanes, which were thoroughly characterized by NMR (1H and 13C) and mass spectrometry. Compound 3a selectively detect Sn(II) metal ion over other relevant metal cations by UV–Visible and fluorometric spectroscopic experiments with low limit of detection (LOD) values of 3.725 × 10−8 M and 4.32 × 10−9 M and binding constant values of 0.479 × 107 M−1 and 1.1802 × 1010 M−1, respectively. Job's plot supports the 1:1 stoichiometric binding of compound 3a to Sn(II) metal ion. Pharmacokinetic properties of the synthesized drugs were also studied using MOLINSPIRATION and ADMET (absorption, distribution, metabolism, excretion, and toxicity) software, and they gave satisfactory results. Good anti-oxidant properties were shown by compound 3a with IC50 value 15 ± 2.07. However, antioxidant therapy has potent benefit in treatment of malaria [1]. As a result, the protein of malaria Plasmodium falciparum was employed in a molecular docking experiment with compound 3a to investigate the compound's potential anti-malarial activity, and it produced extremely good results with a binding energy of -6.43 Kcalmol−1. Furthermore, the compound 3a's recovery of Sn(II) in water samples was tested with a recovery percentage greater than 95 which suggests it can be employed in real time applications.

Assessing the Entomological Parameters of Malaria Vectors in Anambra State, Southeast Nigeria

Adequate knowledge of entomological parameters within a defined geographic endemic area is basic for effective planning of malaria vector control for malaria elimination. The study investigated sibling species of malaria vectors, indoor resting density (IRD), human biting rate (HBR), blood meal source (BMS), human blood index (HBI), sporozoite rate (SR) and entomological inoculation rate (EIR) of malaria vectors in Awka North, Awka South and Njikoka Local Government Areas in Anambra State, southeast Nigeria. Pyrethrum spray collection (PSC), Centre for Disease Control (CDC) light trap, and human landing catch (HLC) techniques were the methods used for collection of indoor and outdoor malaria vectors. Mosquitoes collected were sorted according to species and sex; and identified using standard morphological and molecular techniques. Chi-square test was used for data analysis. A total of 2,870 Anopheles mosquitoes were collected, male 1949 (67.9%) and female 921 (32.1%). All female species identified morphologically belong to the Anopheles gambiae s. l. complex. From the molecular and siblings species separation, Anopheles gambiae recorded the highest abundance of 54.2% and Anopheles coluzzii the least abundance of 45.8%. The IRD was found to be 1.40 per man per night with an average HBR of 5.05. The blood meal source showed that human blood source was the highest number with 46.2%, followed by goat blood source with 32.7%, and combination of human and goat blood was the least with 21.2%. The result also showed a HBI of 0.51 whereas the test for the presence of circumsporozoite protein (CSP) of Plasmodium falciparum shows that none of the malaria vectors was positive for sporozoite; thus, the EIR could not be determined and compared among the study population. The values of the entomological parameters and the allopatric breeding of the two sibling species of Anopheles gambiae and Anopheles coluzzii reported in this study which is probably the second of such report in Nigeria has a huge implications for malaria vector control and malaria control in Anambra State, Southeast Nigeria.