Publications by authors named "R Viswanatha"

48 Publications

Early-stage culprit in protein misfolding diseases investigated using electrochemical parameters: New insights over peptide-membrane interactions.

Biomed Pharmacother 2021 Oct 28;142:111964. Epub 2021 Jul 28.

Department of Applied Chemistry, School of Applied Natural Science, Adama Science and Technology University, P O Box 1888, Adama, Ethiopia. Electronic address:

The dysfunctioning of β-cells caused by the unspecific misfolding of the human islet amyloid polypeptide (hIAPP) at the membrane results in type 2 diabetes mellitus. Here, we report for the first time, the early-stage interaction of hIAPP oligomers on the DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) lipid membrane using electrochemical parameters. Electrochemical techniques are better than other techniques to detect hIAPP at significantly lower concentrations. The surface level interactions between the peptide (hIAPP) and lipid membrane (DMPC) were investigated using atomic force microscopy (AFM), confocal microscopy (CM) and electrochemical techniques such as Tafel polarization, cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Inserting IAPP into the fluid domains results in breaking the lipid-to-lipid interaction, leading to restriction of membrane mobility. The S values of the liposome and IAPP co-solubilized liposome indicates the cooperative insertion of IAPP. Further, a new method of immobilizing a membrane to the gold surface has been employed, resulting in an electrical contact with the buffer, preventing the direct utilization of a steady-state voltage across the bilayer. The electrochemical studies revealed that the charge transfer resistance decreased for 3-mercaptopropanoic acid modified gold (MPA-Au) electrode coated with the liposome and after the addition of IAPP, followed by an increase in the capacitance. The present study has opened up new dimensions to the understanding of peptide-membrane interactions and shows different experimental approaches for the future researchers in this domain.
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http://dx.doi.org/10.1016/j.biopha.2021.111964DOI Listing
October 2021

Maternal and perinatal outcomes of dichorionic diamniotic twins in women after spontaneous and assisted conception.

Eur J Obstet Gynecol Reprod Biol 2021 Aug 1;263:247-251. Epub 2021 Jul 1.

MRCOG, Consultant Fetal Medicine and Divisional Director, Obstetrics and Gynaecology Department, Epsom and St. Helier University Hospitals NHS Trust, Epsom, Surrey, UK. Electronic address:

Objective: Twin pregnancies have been shown to be associated with numerous maternal and perinatal complications. Published data shows conflicting reports on whether assisted conception influences these risks. The purpose of this study was to assess the impact of mode of conception on maternal and perinatal outcomes of dichorionic diamniotic twin pregnancies.

Study Design: This was a large retrospective study of 497 women with dichorionic diamniotic twins that were conceived spontaneously or with assisted conception in a single centre over a 10-year period.

Results: This study showed no significant difference in mode of delivery (OR 1.40 95% CI 0.88 - 2.24), need for admission to neonatal unit (OR 1.56 95% CI 0.88-2.77), or preterm births between dichorionic twin pregnancies conceived following assisted conception when compared to spontaneously conceived dichorionic twin pregnancies. Women who conceived twins by assisted conception that did not have an elective caesarean section were more likely to go into spontaneous labour than have an induction of labour (OR 0.54 95% CI 0.3 - 0.99). They also had a higher chance of having an estimated blood loss of more than 1L than women who conceived naturally (OR 1.70 95% CI 1.06 - 2.73).

Conclusions: In the case of dichorionic twins, this study showed that assisted conception does not seem to be associated with adverse obstetric and perinatal outcomes when compared with spontaneous conception. These results should be considered reassuring to women undergoing assisted conception, and may assist clinicians when counselling patients for assisted conception treatment. Further research is needed to assess the impact of assisted conception on postpartum blood loss.
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http://dx.doi.org/10.1016/j.ejogrb.2021.06.044DOI Listing
August 2021

Magneto-Optical Stark Effect in Fe-Doped CdS Nanocrystals.

Nano Lett 2021 May 27;21(9):3798-3804. Epub 2021 Apr 27.

IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.

Fe doping in II-VI semiconductors, due to the absence of energetically accessible multiple spin state configurations, has not given rise to interesting spintronic applications. In this work, we demonstrate for the first time that the interaction of homogeneously doped Fe ions with the host CdS nanocrystal with no clustering is different for the two spin states and produces two magnetically inequivalent excitonic states upon optical perturbation. We combine ultrafast transient absorption spectroscopy and density functional theoretical analysis within the ground and excited states to demonstrate the presence of the magneto-optical Stark effect (MOSE). The energy gap between the spin states arising due to MOSE does not decay within the time frame of observation, unlike optical and electrical Stark shifts. This demonstration provides a stepping-stone for spin-dependent applications.
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http://dx.doi.org/10.1021/acs.nanolett.1c00126DOI Listing
May 2021

Effector-mediated ERM activation locally inhibits RhoA activity to shape the apical cell domain.

J Cell Biol 2021 Jun;220(6)

Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY.

Activated ezrin-radixin-moesin (ERM) proteins link the plasma membrane to the actin cytoskeleton to generate apical structures, including microvilli. Among many kinases implicated in ERM activation are the homologues LOK and SLK. CRISPR/Cas9 was used to knock out all ERM proteins or LOK/SLK in human cells. LOK/SLK knockout eliminates all ERM-activating phosphorylation. The apical domains of cells lacking LOK/SLK or ERMs are strikingly similar and selectively altered, with loss of microvilli and with junctional actin replaced by ectopic myosin-II-containing apical contractile structures. Constitutively active ezrin can reverse the phenotypes of either ERM or LOK/SLK knockouts, indicating that a central function of LOK/SLK is to activate ERMs. Both knockout lines have elevated active RhoA with concomitant enhanced myosin light chain phosphorylation, revealing that active ERMs are negative regulators of RhoA. As RhoA-GTP activates LOK/SLK to activate ERM proteins, the ability of active ERMs to negatively regulate RhoA-GTP represents a novel local feedback loop necessary for the proper apical morphology of epithelial cells.
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http://dx.doi.org/10.1083/jcb.202007146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8185690PMC
June 2021

CRISPR-based engineering of gene knockout cells by homology-directed insertion in polyploid Drosophila S2R+ cells.

Nat Protoc 2020 10 21;15(10):3478-3498. Epub 2020 Sep 21.

Department of Genetics, Harvard Medical School, Boston, MA, USA.

Precise and efficient genome modifications provide powerful tools for biological studies. Previous CRISPR gene knockout methods in cell lines have relied on frameshifts caused by stochastic insertion/deletion in all alleles. However, this method is inefficient for genes with high copy number due to polyploidy or gene amplification because frameshifts in all alleles can be difficult to generate and detect. Here we describe a homology-directed insertion method to knockout genes in the polyploid Drosophila S2R+ cell line. This protocol allows generation of homozygous mutant cell lines using an insertion cassette which autocatalytically generates insertion mutations in all alleles. Knockout cells generated using this method can be directly identified by PCR without a need for DNA sequencing. This protocol takes 2-3 months and can be applied to other polyploid cell lines or high-copy-number genes.
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http://dx.doi.org/10.1038/s41596-020-0383-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7961850PMC
October 2020
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