Biology subjects

Singha, S.

Publications and source records attributed to Singha, S..

9 recordsLinked to original sources

bioRxiv2026

Photoplethysmography-based glucose estimation with feature selection

Diabetes mellitus is a major global health challenge, and routine blood glucose monitoring still depends on invasive fingerstick sampling. This study examines non-invasive glucose estimation from photoplethysmography (PPG) using a signal quality pipeline and a multi-criteria feature selection framework. PPG recordings from 51 subjects were collected with a custom low-cost system, and 32 passed quality control. Fourteen morphological and autonomic features were extracted and ranked using Pearson and Spearman correlation, partial correlation with confounder adjustment, mutual information and a composite score. The same processing was then applied to a public four-wavelength PPG dataset of 133 subjects with complete metadata, comparing three machine learning input configurations on a held-out test set of 27 subjects. Adding greedy forward-selected PPG features to subject metadata gave a coefficient of determination of 0.410 with Random Forest at 730 nm, compared with 0.355 for metadata alone. Gains at the other wavelengths were at most 0.024, and no significance test was performed. Agreement with the ISO 15197:2013 criterion ranged from 74% to 85%, below the 95% the standard requires. A compact set of amplitude-variability and spectral features may add modest information to demographic predictors, but this needs confirmation in larger cohorts, with longer recordings and independent validation.

bioengineering↗

bioRxiv2026

Meiotic cohesin paralogs govern cell survival by exhibiting flexibility in partner choice

Erroneous loading of the ring-shaped cohesin complex, especially at centromeres, cause chromosomal segregation defects in both mitosis and meiosis. Mitotic cohesin subunits of this complex, either get replaced or co-exist with their meiotic paralogs during meiosis and also in certain cancers. However, it is unclear whether meiotic paralogs can partner mitotic subunits to form hybrid complexes in somatic cells and if there are any functional consequences on cancer progression. Here, we provide a conceptual framework for the principles of cohesin complex assembly involving non-canonical subunits in proliferating Schizosaccharomyces pombe. We show that chromosome loading, segregation fidelity and cellular proliferation are critically affected by the composition of the available cohesin complexes. We find stark differences in the ability of the meiotic kleisin subunit Rec8 to support robust centromere loading, irrespective of its partner, when compared to the canonical mitotic paralog Rad21. Such variations in cellular growth can be explained by different dwell times of these cohesin complexes on the chromosomes as determined by single-molecule tracking and altered chromatin enrichment. We also discover a unique feature of Rec8, in stabilizing chromatin-bound hypomorphic cohesin mutants that aid in cell survival under restrictive conditions. Overall, we highlight the flexibility of meiotic cohesins in restoring function, albeit at a fitness cost, in the presence of inactivating cohesin mutations. Such imbalances could be exploited by cancers to aid cell survival, but at the expense of increased aneuploidy and genomic instability.

molecular biology↗

bioRxiv2026

Inhibition of mucin-type O-glycosylation impairs melanogenesis, melanoma growth, and metastatic capacity

Tumor-associated glycans are critical regulators of immune evasion in melanoma. Despite the success of immune checkpoint blockade, resistance and relapse remain a challenge, highlighting the need to therapeutically target additional immunosuppressive axes. One such axis involves Siglec-sialoglycan interactions that facilitate tumor immune evasion. The melanoma-associated antigen Pmel17/gp100 is a melanosomal glycoprotein overexpressed in tumor cells and essential for melanosomal architecture. Pmel17/gp100 forms amyloid fibrils within melanosomes, and its extensive O-glycosylation contributes to melanin biosynthesis and melanoma progression. We show that pharmacological inhibition of O-glycosylation using peracetyl N-thioglycolyl-D-galactosamine (Ac5GalNTGc, 1a) decreases Pmel17/gp100 glycosylation and melanin synthesis in B16F10 melanoma cells, induces tumor surface hyposialylation, diminishes Siglec-E engagement, and disrupts the Siglec-sialoglycan immune checkpoint. In C57BL/6J mice, 1a significantly delayed tumor growth, prolonged survival, and reduced lung metastases relative to controls. These findings identify O-glycosylation as a dual-mode therapeutic vulnerability, linking melanosome dysfunction to attenuation of Siglec-mediated immune evasion in melanoma. SummaryMucin-type O-glycans on melanoma cell surfaces and the melanosomal protein, Pmel17/gp100, regulate melanogenesis and melanoma metastasis. The O-glycosylation inhibitor, peracetyl N-thioglycolyl-D-galactosamine (Ac5GalNTGc, 1a), suppressed melanin synthesis and induced hyposialylation, thereby disrupting Siglec-mediated immune evasion and retarding tumor growth and metastasis.

cancer biology↗

bioRxiv2025

Phosphorylation-inducing molecules for regulating dynamic cellular processes

Dynamic cellular processes often employ protein phosphorylation for rapid information transfer within and between cells. Phosphorylation-inducing chimeric small molecules (PHICS) have been developed for targeted protein phosphorylation by on-demand inducing a kinase-protein pairing. However, widespread application of PHICS has been limited as previously reported PHICS that recruited AMP-activated protein kinase (AMPK) required serum starvation and target protein overexpression, recruited only a few of the potential AMPK complexes, and exhibited poor dose- and temporal control. Herein, we report an AMPK PHICS platform that operates under physiological conditions (i.e., no serum starvation or target overexpression), recruits multiple AMPK complexes, and can induce target protein phosphorylation with dose and temporal control. We demonstrated the utility of this platform for controlling phosphorylations that underlie two dynamic cellular processes, namely oncogenic signaling and phase separation. An AMPK PHICS directed against Brutons Tyrosine Kinase (BTK), which is a driver of several B cell malignancies, was effective at inducing the death of drug-resistant cancer cells. Here, PHICS induced inhibitory phosphorylations on BTK and attenuated its oncogenic pathway. Phosphorylation of Liprin-3 induces phase separation in neurons and is critical for neurotransmitter release. Using AMPK PHICS that phosphorylated Liprin-3, we induced Liprin-3 phase separation with dose and temporal control. We envision this PHICS platform to find utility in inducing and controlling protein phosphorylations for basic research and biomedicine. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/652895v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@16bbb20org.highwire.dtl.DTLVardef@1ca5267org.highwire.dtl.DTLVardef@1e805d5org.highwire.dtl.DTLVardef@1d6ec22_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2023

Development and applications of chimera platforms for tyrosine phosphorylation

Chimeric small molecules that induce post-translational modification (PTM) on a target protein by bringing it in proximity to a PTM-inducing enzyme are furnishing novel modalities to perturb protein function. Despite recent advances, such molecules are unavailable for a critical PTM, tyrosine phosphorylation. Furthermore, the contemporary design paradigm of chimeric molecules, formed by joining a non-inhibitory binder of the PTM-inducing enzyme with the binder of the target protein, prohibits the recruitment of most PTM-inducing enzymes as their non-inhibitory binders are unavailable. Here, we report two platforms to generate phosphorylation-inducing chimeric small molecules (PHICS) for tyrosine phosphorylation. We generate PHICS from both non-inhibitory binders (scantily available, platform 1) and kinase inhibitors (abundantly available, platform 2) using cysteine-based group transfer chemistry. PHICS triggered phosphorylation on tyrosine residues in diverse sequence contexts and target proteins (e.g., membrane-associated, cytosolic) and displayed multiple bioactivities, including initiation of a growth receptor signaling cascade and death of drug-resistant cancer cells. These studies provide an approach to induce biologically relevant PTM and lay the foundation for pharmacologic PTM editing (i.e., induction or removal) on target proteins using abundantly available inhibitors of PTM-inducing or erasing enzymes. TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/531183v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@cdf529org.highwire.dtl.DTLVardef@19a70cdorg.highwire.dtl.DTLVardef@63dbf9org.highwire.dtl.DTLVardef@1febaaf_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2020

The hepatic compensatory response to elevated systemic sulfide impairs medium chain fat oxidation and promotes diabetes

Impaired hepatic glucose and lipid metabolism are hallmarks of type-2 diabetes. Increased sulfide production from cysteine, or sulfide-donor compounds, may beneficially regulate hepatic metabolism. Disposal of sulfide through the sulfide oxidation pathway (SOP) is critical for maintaining sulfide within a safe physiological range. We show that mice lacking the liver-enriched mitochondrial SOP enzyme thiosulfate sulfur-transferase (Tst-/- mice) exhibit high circulating sulfide, increased gluconeogenesis, hypertriglyceridemia and fatty liver, despite whole-body insulin-sensitisation. Unexpectedly, hepatic sulfide levels were normal in Tst-/- mice, a result of homeostatic induction of mitochondrial sulfide disposal and glutathione excretion associated with net suppression of protein persulfidation and nuclear respiratory factor-2 target proteins. Proteomic and persulfidomic profiling converged on gluconeogenesis and hepatic lipid metabolism and revealed a selective deficit in medium-chain fatty acid oxidation in Tst-/- mice. We reveal a critical role for TST in hepatic metabolism that raises implications for sulfide-donor strategies in the context of liver function and metabolic disease.

physiology↗

bioRxiv2017

Cross talk between photo-pigments and graphene electron cloud - Designing a biodiode

We report emergence of a new electrical material by growing photosynthetic biofilm on a Dirac material, graphene. The material showed new conducting as well as semiconducting properties. Frequency dependent capacitive spectra further indicated presence of electrical isosbestic points(at 0.8 and 9MHz), implying two state dieletric transitions at critical frequencies. A notable reult was a Schottky diode like behavior in the IV curve. Voltage dependent conductance with conductance peaks near the Schottky diode threshold was observed. We obtained facilitated growth of photosynthetic biofilm in presence of graphene. Lastly higher bacterial metabolism was seen in graphene incorporated biofilm. For this zero band gap Dirac material this can only be interpreted as coupling of the electron transport chain of the bacterial biofilm and the graphene electron cloud.

biophysics↗

bioRxiv2017

Cooling Induced by Uphill Energy Transport in Plant Photosystems

The uphill energy transfer in photosystems implies input energy at higher wavelength leading to energy output at lower wavelength. Briefly, energy is uphill transported from photosystem I (PSI) to photosystem II (PSII), the latter having a lower wavelength emission. This uphill energy transport involves absorption of thermal energy from the surroundings. While such cooling effects have been reported in laser systems we report for the first time a white light driven cooling in thylakoid suspension. The cooling of the surrounding medium by appropriate illumination was illustrated using thermal measurements. Again cooling is inhibited by agents like 3-(3,4-Dichlorophenyl)-1,1-dimethylurea,that block the linear electron flow between the photocenters, implying a dependence of the cooling on interplay between such centers. Furthermore, it is possible to modulate the cooling pattern by addition of external agents like nanopaticles, some favoring further cooling (e.g., Ag nanoparticle) and some like Au or chlorophyll nanoparticles, showing insignificant or even reverse trends. Interestingly, the cooling is invariably associated with the 77K spectra of the thylakoid suspension. With reference to the dark control, an agent causing cooling always increases PSII to PSI ratio and vice versa i.e.,the uphill energy transport. Importantly, the cooling effect, apart from its import role in plant physiology can be exploited artificially for energy saving in post-harvest or food preservation.

bioengineering↗

bioRxiv2017

Emerging Electrical Properties of Graphene incorporated Photosynthetic Biofilms

We report emergence of a new electrical material by growing photosynthetic biofilm on a Dirac material, graphene. The material showed new conducting as well as semiconducting properties. Frequency dependent capacitive spectra further indicated presence of electrical isosbestic points(at 0.8 and 9MHz), implying two state dieletric transitions at critical frequencies. A notable reult was a Schottky diode like behavior in the IV curve. Voltage dependent conductance with conductance peaks near the Schottky diode threshold was observed. We obtained facilitated growth of photosynthetic biofilm in presence of graphene. Lastly higher bacterial metabolism i was seen in the biofilm in contact with graphene as compared to its normal growth condition. For this zero band gap Dirac material this can only be interpreted as coupling of the electron transport chain of the bacterial biofilm and the graphene electron cloud.

biophysics↗