Biology subjects

Pawlak, K.

Publications and source records attributed to Pawlak, K..

3 recordsLinked to original sources

bioRxiv2026

SMART-NeuroDx: A Reagent-Free Multianalyte Biosensor Platform with Machine-Learning Readout for Point-of-Care Dementia Screening

Differentiating overlapping dementia pathologies, such as frontotemporal dementia and Alzheimers disease, calls for the simultaneous measurement of several blood biomarkers, yet electrochemical sensors remain predominantly single-target and dependent on labels and sample preparation. Here we report SMART-NeuroDx, a reagent-free electrochemical array that quantifies pTau217, GFAP, pTau181, and NfL directly from unprocessed plasma and serum in under 35 minutes. Four surface-confined redox-active molecularly imprinted polymer and aptamer-MIP recognition matrices are electropolymerized onto a four-working-electrode porous-gold printed-circuit array, using potential-assisted electrostatic gating keyed to each targets isoelectric point to prevent cross-channel template contamination during synthesis. Label-free Faradaic responses from the redox-active polymer backbone are acquired on a custom battery-powered STM32G4 handheld potentiostat and converted to concentration from five voltammetric features using cross-validated Random Forest and XGBoost regressors. The handheld unit reproduced the baseline fidelity of a commercial benchtop workstation and resolved sub-picogram pTau217 (limit of detection 0.087 pg mL-{superscript 1}) across marker-appropriate dynamic ranges, with inter-chip relative standard deviation at or below 5.34% and coefficients of determination of 0.94 to 0.99 against reference concentrations. Each channel retained selectivity in plasma and serum against competing neurological and inflammatory proteins, with non-specific signal deviation held below 10% by the hydrated PyPEG interfacial shell. The platform establishes reagent-free, simultaneous four-analyte neurodegeneration sensing on a single point-of-care device.

bioengineering↗

bioRxiv2026

Spatiotemporal biogenesis of thylakoid membranes in the green alga Chlamydomonas reinhardtii

Thylakoid membranes are essential for oxygenic photosynthesis, yet the mechanisms underlying their spatial and temporal biogenesis remain poorly understood. Here, using a light-induced membrane regeneration system in Chlamydomonas reinhardtii, we generate a time-resolved map of thylakoid formation and photosynthetic complex assembly at unprecedented spatial and temporal resolution by integrating super-resolution fluorescence microscopy, cryo-electron tomography, proteomics, and spectroscopy. We show that thylakoid biogenesis is globally distributed and multipolar, with new membrane formation occurring at multiple sites across the chloroplast, including regions adjacent to the inner envelope membranes in both basal and lobe regions. We identify F-ATP synthase storage membranes and map the redistribution of translating ribosomes from T-zone enrichment to a chloroplast-wide distribution at early stages of thylakoid formation, consistent with decentralized synthesis of photosynthetic complexes. We further delineate the hierarchical assembly of photosystem supercomplexes, starting with formation of reaction centers. Together, these findings refine the spatial organization of photosynthetic membrane biogenesis and establish a unified spatiotemporal framework linking thylakoid formation, translational activation, and functional maturation, providing a mechanistic basis for plastid engineering to enhance photosynthetic efficiency.

Cell Biology↗

bioRxiv2025

Synthesis of C8-vinyl chlorophylls d and f impairs far-red light photoacclimation and growth under far-red light

The inducible biosynthesis of chlorophylls d and f enables a subset of specialised cyanobacteria to perform oxygenic photosynthesis under far-red light--in the absence of visible wavelengths--via a process termed far-red light photoacclimation. These pigments, like the more common chlorophylls a and b, typically carry an ethyl substituent at the C8 position of the macrocycle, formed by reduction of a vinyl group by an 8-vinyl reductase enzyme. Here, we disrupted the gene encoding BciB, an 8-vinyl reductase found in the majority of cyanobacteria, in Chroococcidiopsis thermalis PCC 7203, a model for the study of far-red light photoacclimation. Disruption of bciB results in the synthesis of 8-vinyl chlorophyll a when the cells are grown in white light; on switching to far-red light, synthesis of 8V-forms of chlorophylls d and f, which have not been detected in nature, are synthesised in this strain. The bciB mutant exhibits sensitivity to high irradiance under both light regimes. Pigment analysis and whole-cell absorption and fluorescence spectroscopy reveal decreased synthesis of far-red absorbing chlorophylls, reduced photosystem assembly and an impaired acclimation to far-red light, and transmission electron microscopy demonstrates altered thylakoid membrane morphology in the mutant when compared to the wild type. These results demonstrate the importance of 8-vinyl group reduction for acclimation to far-red light.

biochemistry↗