Browsing by Author "Kumar, N"

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    Probing into crystallography and morphology properties of MoS2 nanoflowers synthesized via temperature depend enthydro thermal method
    (2022-07) Kumar, N; Siroha, P; Shankar, H
    This paper reports the formation of flower-like hierarchical molybdenum disulfide(MoS2) nanoparticles following a simple one-step hydrothermal process with varying temperatures(200°C and220°C).The as-synthesized particles were examined crystallo graphically by X-ray diffraction (XRD) method which revealed the formation of hexagonal MoS2(2H-MoS2)and that the crystallite size of the particles increased with increasing hydro thermal temperature. Surface morphological characteristics of the particles were investigated by a field emission scanning electron microscope (FESEM)and interesting details were revealed such as the rounded 3D flower-like microstructure of the MoS2 particles and the petals of the flowers were composed of plate lets built up by stacked-up MoS2 nano sheets. With the increase in hydro thermal temperature ,the interlayer spacing of stacked layers of intense (002) plane is slightly decreased although the crystallinity of the materials improved. Both diameter and thickness of the nanoflowers and then a no plate lets increased twice with increasing the temperatures. A visual crystallographic perspective was presented through simulation of 3D wire frame unit cell as sociated with the individual lattice planes as observed in the XRD pattern of the samples. In addition, a plausible growth mechanism is proposed for the formation of the obtained MoS2 nanoflowers on the basis of experimental observations and analysis.
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    Ydj1 interaction at nucleotide-binding-domain of yeast Ssa1 impacts Hsp90 collaboration andclient maturation
    (2022-11) Gaur, D; Kumar, N; Ghosh, A; Singh, P; Kumar, P; Guleria, J; Kaur, S; Malik, N
    Hsp90constitutes one of the major chaperone machinery in the cell. The Hsp70 assists Hsp90inits client maturation though the underlying basis of the Hsp70 role remains to be explored. In the present study, using S. cerevisiae strain expressing Ssa1 as sole Ssa Hsp70, weidentified novel mutations in the nucleotide-binding domain of yeast Ssa1 Hsp70 (Ssa1-T175N andSsa1-D158N)that adversely affect the maturation of Hsp90 clients v-Src andSte11. The identified Ssa1 amino acids critical for Hsp90 function were also found to be conserved across species such as in E.coli DnaK and the constitutive Hsp70 isoform (HspA8) in humans. These mutations are distal to the C-terminus of Hsp70, that primarily mediates Hsp90 interaction through the bridge protein Sti1, and proximal to Ydj1 (Hsp40 co chaperone of Hsp70 family) binding region. Intriguingly, we found that the bridge protein Sti1 is critical for cellular viability in cells expressing Ssa1-T175N (A1-T175N) or Ssa1 D158N(A1-D158N)assoleSsaHsp70.Thegrowthdefectwasspecific forsti1Δ,as deletion of none of the other Hsp90 co-chaperones showed lethality in A1-T175N or A1-D158N. Mass-spectrometry based whole proteome analysis of A1-T175N cells lacking Sti1 showed an altered abundance of various kinases and transcription factors suggesting compromised Hsp90activity. Further proteomic analysis showed that pathways involved in signaling, sig nal transduction, and protein phosphorylation are markedly downregulated in the A1-T175N upon repressing Sti1 expression using doxycycline regulatable promoter. In contrast to Ssa1, the homologous mutations in Ssa4 (Ssa4-T175N/D158N), the stress inducible Hsp70 isoform, supported cell growth even in the absence of Sti1. Overall, our data suggest that Ydj1 competes with Hsp90 for binding to Hsp70, and thus regulates Hsp90 interaction with the nucleotide-binding domain of Hsp70. The study thus provides new insight into the Hsp70-mediated regulation of Hsp90 and broadens our understanding of the intricate com plexities of the Hsp70-Hsp90 network.