Biology subjects

Pyne, A.

Publications and source records attributed to Pyne, A..

4 recordsLinked to original sources

bioRxiv2026

Denatured Albumin Gains a Function of Regulating Platelet Activity

Platelets are blood cells that play a critical role in hemostasis and thrombosis. Serum albumin, which constitutes approximately 50% of plasma proteins, has traditionally been considered non-interactive with platelets and not involved in platelet function. Here, using a molecular force sensor and platelet adhesion and aggregation assays, we show that serum albumin, if denatured, specifically binds to integrin IIb{beta}3 in platelets and transmits platelet contractile forces, regulating platelet activation, adhesion and aggregation as effectively as fibrinogen (the clotting factor I). 0.1% ethanol or 10 {micro}M hydrogen peroxide, physiologically attainable in blood through alcohol intake or disease-elevated oxidative stress, are sufficient to denature albumin into a functional platelet ligand. These findings revealed albumin as a previously unrecognized but important regulator of platelet functions, with broad implications for the thrombotic risk in the context of physiological conditions that induce albumin denaturation.

cell biology↗

bioRxiv2026

Digest before Ingest: Early Recruitment of Membrane-bound DNaseX to Phagocytic Cups in Macrophages

Macrophages engulf and degrade pathogens and cellular debris through phagocytosis. The degradation process was generally believed to occur only after phagosome internalization and maturation. Here, we report an early DNase activity at the nascent phagocytic cup (PC) prior to its closure. Using a fluorescent DNase sensor, we revealed rapid and ubiquitous DNase activity upon PC formation across various macrophage types. We further identified the responsible enzyme as the membrane-bound DNaseX, which is constitutively recruited to the PC during PC formation. F-actin polymerization was found to correlate with DNase activity in the PC, likely by promoting physical engagement of DNaseX with solid DNA materials. Functionally, we show that macrophages degrade extracellular DNA (eDNA) within bacterial biofilms through direct physical contact, clearing the eDNA structures without internalization. These findings reveal a previously unrecognized DNA degradation mechanism operating at the macrophage membrane, suitable for degrading bulky eDNA materials which cannot be directly internalized by macrophages.

cell biology↗

bioRxiv2019

Imaging live bacteria at the nanoscale: comparison of immobilisation strategies

Atomic force microscopy (AFM) provides an effective, label-free technique enabling the imaging of live bacteria under physiological conditions with nanometre precision. However, AFM is a surface scanning technique, and the accuracy of its performance requires the effective and reliable immobilisation of bacterial cells onto substrates. Here, we compare the effectiveness of various chemical approaches to facilitate the immobilisation of Escherichia coli onto glass cover slips in terms of bacterial adsorption, viability and compatibility with correlative imaging by fluorescence microscopy. We assess surface functionalisation using gelatin, poly-L-lysine, Cell-Tak, and Vectabond(R). We describe how bacterial immobilisation, viability and suitability for AFM experiments depend on bacterial strain, buffer conditions and surface functionalisation. We demonstrate the use of such immobilisation by AFM images that resolve the porin lattice on the bacterial surface; local degradation of the bacterial cell envelope by an antimicrobial peptide (Cecropin B); and the formation of membrane attack complexes on the bacterial membrane.

biophysics↗

bioRxiv2019

PEGylated surfaces for the study of DNA-protein interactions by atomic force microscopy

DNA-protein interactions are vital to cellular function, with key roles in the regulation of gene expression and genome maintenance. Atomic force microscopy (AFM) offers the ability to visualize DNA-protein interactions at nanometre resolution in near-physiological buffers, but it requires that the DNA be adhered to the surface of a solid substrate. This presents a problem when working at biologically relevant protein concentrations, where protein may be present at large excess in solution; much of the biophysically relevant information can therefore be occluded by non-specific protein binding to the underlying substrate. Here we explore the use of PLLx-b-PEGy block copolymers to achieve selective adsorption of DNA on a mica surface. Through varying both the number of lysine and ethylene glycol residues in the block copolymers, we show selective adsorption of DNA on mica that is functionalized with a PLL10-b-PEG113 / PLL1000-2000 mixture as viewed by AFM imaging in a solution containing high concentrations of streptavidin. We show that this selective adsorption extends to DNA-protein complexes, through the use of biotinylated DNA and streptavidin, and demonstrate that DNA-bound streptavidin can be unambiguously distinguished by in-liquid AFM in spite of an excess of unbound streptavidin in solution.

biophysics↗