Biology subjects

Nolan, K.

Publications and source records attributed to Nolan, K..

4 recordsLinked to original sources

bioRxiv2025

Extraordinary activation of CALB by alkylammonium ions: a new paradigm for activity enhancement of enzymes

Candida antarctica lipase B (CALB) is widely used in biocatalysis with applications in plastics degradation and chemical synthesis. CALB is activated by hydrophobic matrices and, enigmatically, shows striking activation in polar, choline-based, Deep Eutectic Solvents (DES). Herein, we show that CALB activation and stabilisation by TAAs is caused by binding to cholines tetraalkylammonium (TAA) moiety. Several related TAA salts also caused CALB activation which was proportional to the hydrophobicity of their alkyl substituents. Remarkably, tetraoctylammonium bromide showed activation of [~]500% even at low micromolar levels. These TAA salts represent a new class of enzyme activator. Molecular modelling identified the alkylammonium binding location as a hydrophobic patch centred around Asp-145 of CALB. Binding at this site explains lipase activation in polar DES solvents and its relationship to other pathways of CALB activation. Herein, we also demonstrate that CALB, like many lipases, is activated by calcium. Intriguingly, mixed soluble activator experiments showed that calcium and choline bind to different CALB sites, suggesting a two-site model for CALB activation. These observations, along with previous findings, show that TAA activation is a widespread property of enzymes and constitutes a novel and potent means to enhance enzyme turnover and stability. HighlightsO_LICALB is activated by choline C_LIO_LISeveral tetraalkylammonium salts cause activation of CALB C_LIO_LIHyperactivation of CALB (5-fold) by tetraoctylammonium ions occurs at low micromolar concentrations. C_LIO_LITwo independent sites for CALB activation, by calcium and TAA ions, are identified C_LIO_LIActivation at the choline binding site stabilises CALB while calcium binding destabilises the enzyme C_LIO_LIA soluble activator is demonstrated, that can be used to probe the activation mechanism of CALB or other enzymes. C_LI

bioengineering↗

bioRxiv2023

Development of a Nanoparticle-Based Tendon-Targeting Drug Delivery System to Pharmacologically Modulate Tendon Healing

Tendon regeneration following acute injury is marred by a fibrotic healing response that prevents complete functional recovery. Despite the high frequency of tendon injuries and the poor outcomes, including functional deficits and elevated risk of re-injury, there are currently no pharmacological therapies in clinical use to enhance the healing process. Several promising pharmacotherapies have been identified; however, systemic treatments lack tendon specificity, resulting in poor tendon biodistribution and perhaps explaining the largely limited beneficial effects of these treatments on the tendon healing process. To address this major unmet need, we leveraged our existing spatial transcriptomics dataset of the tendon healing process to identify an area of the healing tendon that is enriched for expression of Acp5. Acp5 encodes tartrate-resistant acid phosphatase (TRAP), and we demonstrate robust TRAP activity in the healing tendon. This unexpected finding allowed us to refine and apply our existing TRAP binding peptide (TBP) functionalized nanoparticle (NP) drug delivery system (DDS) to facilitate improved delivery of systemic treatments to the healing tendon. To demonstrate the translational potential of this drug delivery system, we delivered the S100a4 inhibitor, Niclosamide to the healing tendon. We have previously shown that genetic knockdown of S100a4 enhances tendon healing. While systemic delivery of Niclosamide did not affect the healing process, relative to controls, TBP-NP delivery of Niclosamide enhanced both functional and mechanical outcome measures. Collectively, these data identify a novel tendon-targeting drug delivery system and demonstrate the translational potential of this approach to enhance the tendon healing process.

bioengineering↗

bioRxiv2022

Pericyte Heterogeneity Identified by 3D Ultrastructural Analysis of the Microvessel Wall

ABSTRACT/SUMMARYUnequivocal pericyte identification remains a limitation in the field of vascular biology given the lack of unique molecular marker. Compounding this challenge are the recently described heterogeneities in pericyte morphology across microvascular networks. Here, we found further support on the ultrastructural level for classifying pericytes into sub-types - "thin-strand" (TSPs), mesh (MP), and ensheathing (EP) pericytes - based on their architecture in the mouse brain microcirculation. We also observed several instances of an additional cell type in the medial layer between endothelial cells and pericytes, specifically associated with EPs. A conserved characteristic across PC subtypes was extracellular matrix (ECM) encompassing the vascular unit and dispersed among neighboring cells. ECM thicknesses fell within a specific range depending on vessel location, and only thinned where cells were in closer proximity. Pericytes and endothelial cells formed "peg-and-socket" structures at these locations, providing another distinguishing feature across PC subtypes. Unique contact locations seemed to be present between medial and endothelial cells, as well as between vascular cells and the brain parenchyma. The ECM surrounding EPs exhibited another notable configuration in that thin extensions radiated out from the vessel wall into the surrounding parenchyma, suggesting mechanical and/or biochemical roles. Considering these data together, ultrastructural observations may provide an orthogonal perspective on pericyte heterogeneity and the presence of medial cells in cerebrovascular walls as well as assessing ECM coverage as a criterion for PC identification and exploring PC-associated ECM extensions that may have unique relevance in health and disease.

cell biology↗

bioRxiv2021

Self-regulation of the brain's Beta rhythm using a brain-computer interface improves inhibitory control

Neural oscillations, or brain rhythms, fluctuate in a manner reflecting ongoing behavior. Whether these fluctuations are instrumental or epiphenomenal to the behavior remains elusive. Attempts to experimentally manipulate neural oscillations exogenously using non-invasive brain stimulation have shown some promise, but difficulty with tailoring stimulation parameters to individuals has hindered progress in this field. We demonstrate here using electroencephalography (EEG) neurofeedback in a brain-computer interface that human participants (n=44) learned over multiple sessions across a 6-day period to self-regulate their Beta rhythm (13-20 Hz) over the right inferior frontal cortex (rIFC). The modulation was evident only during neurofeedback task performance but did not lead to offline alteration of Beta rhythm characteristics at rest, nor to changes in subsequent cognitive behavior. Likewise, a control group (n=38) who underwent training of the Alpha rhythm (8-12 Hz) did not exhibit behavioral changes. Although the right frontal Beta rhythm has been repeatedly implicated as a key component of the brains inhibitory control system, the present data suggest that its manipulation offline prior to cognitive task performance does not result in behavioral change. Thus, this form of neurofeedback training of the tonic Beta rhythm would not serve as a useful therapeutic target for disorders with dysfunctional inhibitory control as their basis.

neuroscience↗