Herein, an electrochemical biosensor has been prepared to assess the sensitivity of an organophosphate insecticide, malathion, to acetylcholinesterase (AChE) enzyme of three insects including Apis mellifera (honeybee), Tribolium castaneum (red flour beetle), and Zootermopsis nevadensis (dampwood termite). A composite of nickel chromite (NiCr₂O₄) and graphitic carbon nitride (g-C₃N₄) was prepared and characterized for its morphological, chemical and electrical properties. The NiCr₂O₄/g-C₃N₄ composite integrated pencil graphite electrodes were used to covalently immobilize insect AChE enzymes and amperometric response of bioelectrodes was determined through cyclic voltammetry. The prepared bioelectrodes exhibited high enzyme immobilization efficiency and electro-catalytic performance. The integrated bioelectrodes could efficiently detect malathion induced inhibition of insects' AChEs. The linear ranges for malathion were found to be 0.1–1.6 μM, 1–40 nM and 2–100 nM, and LODs were 2 nM, 0.86 nM and 2.3 nM for A. mellifera, T. castaneum, and Z. nevadensis, respectively. Additionally, the biosensing platform developed using A. mellifera AChE was found highly sensitive and effective for malathion recoveries from spiked wheat flour samples with high recovery rates. Moreover, the proposed method was adequately reproducible and selective. The results revealed that A. mellifera AChE is less sensitive to inhibition by malathion as compared to T. castaneum, and Z. nevadensis AChE. The experimental results were validated through computational docking of malathion with insect AChEs and the results were in correspondence to experimental outcomes. The proposed method can be a plausible alternate to conventional analytical methods to assess the pesticide sensitivity and toxicity of various compounds against insect enzymes.

Growth hormone (GH) variants have been studied for the structure- function relationship of the molecule. The presence of a potential alternate splicing point inmRNA in bGH gene at exon 3, similar to hGH has been reported by workers. Earlyinvestigation on the characteristics of the chemistry of 20k oGH showed that themolecule was produced by site-directed mutagenesis by deleting amino acid residues33-46 and the resultant DNA was expressed in E. coli under the control of lac promoterin pUC based plasmid. The mutant protein remained insoluble and did not refold. Toinvestigate the effect of deletion on the chemistry of the molecule, computationalbiology tools were employed. The mutant with the deletion of amino acid residues 33 46, was designed and the model was visualized on computer. The structure of 20kbGH was compared with bGH and dissected for hydrogen bonds and hydro-phobicity. Computational biology tools were helpful in elucidating the role of 33-46 amino acidresidues domain in the chemistry of the molecule. Furthermore, it was revealed thatremoval of amino acid residues 33-​46 which formed the hydrogen bonds involving Glu33, Gln 46, Pro 38, Arg 42, Tyr 43,Ala 51, Thr 48, Asn 47, led to the formation of newhydrogen bonds between Thr 33, Tyr 144, Asn 32, Asn 32 andSer and Asp 153. Theremoval of the amino acids 33-46 decreased the hydro phobicity of the first helix ofbGH molecule, ascompared to 20k hGH, thus altering the solubility of themolecule, confirming the earlier reported results for ovine growth hormone with samedeletion. Key words: Ovine growth hormone, 20k hGH, hydro-phobicity.