Biology subjects

Roychoudhury, A.

Publications and source records attributed to Roychoudhury, A..

6 recordsLinked to original sources

bioRxiv2026

A Statistical Approach to Cellular Resource Allocation Models

Understanding how cells regulate growth despite molecular complexity remains a central question in quantitative biology. While thousands of genes respond to environmental perturbations, the population growth rate varies smoothly across conditions, suggesting the existence of simple organizing principles. Here, we show that statistical analysis of mRNA composition across environmental conditions reveals growth tradeoffs across organisms including E. coli and S. pombe. Using partial least squares regression, we identify two opposing gene sectors whose coordinated expression encodes growth rate. A minimal transcription-translation model, constrained by empirical scaling laws of total mRNA and ribosomal fractions, explains this tradeoff as a necessary consequence of the empirical observations. Extending the model to include charged tRNA dynamics reveals distinct regulatory regimes: E. coli operates co-limited by ribosomal mRNA and charged tRNA availability, whereas S. cerevisiae is primarily ribosomal mRNA-limited. Together, these results provide a statistical method to determine key tradeoffs across organisms and offer a framework to interpret organism-specific growth regimes.

cell biology↗

bioRxiv2025

Metabolomics-informed coarse-grained model enables prediction of cell-free protein expression dynamics

Cell-free expression systems have gained considerable attention for their potential in biomanufac-turing, biosensing, and circuit prototyping. All these endeavors make use of the innate metabolic activity of cell lysates. However, our knowledge of the underlying nature of cell-free metabolism remains lacking. In this work, we use non-targeted mass spectrometry to generate time-course measurements of small molecules in E. coli cell lysates (metabolomics) during cell-free protein synthesis (CFPS) to show that the majority of E. colis metabolism is active in cell lysate. Fur-thermore, these data indicate that protein synthesis is a relatively small metabolic burden on cell lysates compared to the background metabolism, and that the build-up of multiple metabolic waste products is fundamentally responsible for stopping cell-free protein expression as opposed to depletion of fuel sources. We use these insights coupled with high-throughput CFPS experiments to develop a foundational coarse-grained mechanistic model of CFPS which we show can be easily recalibrated using Bayesian parameter inference techniques to provide accurate models across hundreds of novel experimental conditions. This work provides new experimental insights into the effects of cell-free metabolism on CFPS and establishes a novel framework for leveraging existing CFPS models in new experimental contexts, opening the avenue to future cell-free applications aimed at building complex systems, from multilayered biological circuits to synthetic biological cells.

synthetic biology↗

bioRxiv2025

Influence of simplifications on FE modelling of mandible and TMJ implants

End-stage temporomandibular joint (TMJ) disorders often necessitate joint replacement to restore bilateral mastication. Patient-specific TMJ implants typically rely on detailed in silico modelling derived from subject-specific computed tomography (CT) scans of the mandible. However, generating highly detailed finite element (FE) models is computationally expensive. Although structural simplifications of the mandible are known to influence mechanical behaviour, their quantitative impact on TMJ implant evaluation has not been systematically investigated. This study examines the influence of three modelling simplifications on stress-strain predictions in intact and implanted mandibles: (i) a detailed segmented mandible with tissue-specific material properties (Model 1), (ii) a simplified mandible comprising cortical bone only (Model 2), and (iii) a further simplified mandible excluding dental crowns (Model 3). Both narrow and standard TMJ implants were analysed under osseointegrated and non-osseointegrated conditions, resulting in fifteen FE models. Physiological clenching activities were simulated. Compared with the detailed model, simplified models showed reductions of up to 50% in maximum principal strain in bone and up to 44% in von Mises stress in TMJ implants, while preserving spatial stress-strain trends. These findings indicate that simplified models may be suitable for preliminary implant design, whereas detailed FE modelling remains essential for final pre-clinical evaluation.

bioengineering↗

bioRxiv2024

Biomechanical Evaluation of Temporomandibular Joint Implants Under Complete Mastication Cycle

To ensure the long-term success of temporomandibular joint (TMJ) implants, it is imperative to understand their biomechanical performances. This study aims to compare the biomechanical performance of two stock implants (narrow and standard) under unilateral and bilateral clenching during both osseointegrated and non-osseointegrated conditions. Finite element models of a human mandible were developed from QCT data, with the left TMJ being replaced by the implants. Six clenching tasks were simulated to evaluate stress and strain distributions in the mandible and implants. Ipsilateral clenching produced higher mandibular strains, while contralateral clenching generated larger implant stresses. Furthermore, intercuspal biting was found to have produced the highest strain (1750-1880 {micro}{varepsilon}) and stress ([~]17 MPa) in the mandible. Osseointegration reduced stresses (up to 0.14 MPa) and strains (up to 30 {micro}{varepsilon}) in mandible as well as stresses in mandibular components (up to 48 MPa) and screws (up to 71 MPa). However, during non-osseointegrated conditions, stresses in cortical bone were higher for standard TMJ implant as compared to narrow implant. This suggests possible preference of narrow implant over standard ones.

bioengineering↗

bioRxiv2019

Selective Ablation of Cancer Cells with Low Intensity Pulsed Ultrasound

Ultrasound can be focused into deep tissues with millimeter precision to perform non-invasive ablative therapy for diseases such as cancer. In most cases, this ablation uses high intensity ultrasound to deposit non-selective thermal or mechanical energy at the ultrasound focus, damaging both healthy bystander tissue and cancer cells. Here we describe an alternative low intensity pulsed ultrasound approach that leverages the distinct mechanical properties of neoplastic cells to achieve inherent cancer selectivity. We show that when applied at a specific frequency and pulse duration, focused ultrasound selectively disrupts a panel of breast, colon, and leukemia cancer cell models in suspension without significantly damaging healthy immune or red blood cells. Mechanistic experiments reveal that the formation of acoustic standing waves and the emergence of cell-seeded cavitation lead to cytoskeletal disruption, expression of apoptotic markers, and cell death. The inherent selectivity of this low intensity pulsed ultrasound approach offers a potentially safer and thus more broadly applicable alternative to non-selective high intensity ultrasound ablation.

bioengineering↗

bioRxiv2018

Direct Measurement of Dissipation in a Single Protein using Small Amplitude Atomic Force Microscopy

In Krammers theory, stiffness and dissipation coefficient of a protein determine the rate of their conformational change. Using atomic force microscope, it is possible to measure viscoelasticity of a single protein, wherein its dissipative and elastic nature is directly and independently measured. Such measurements are performed, either by measuring the thermal fluctuations of the protein held under a constant force, or by providing small modulations to the protein by dithering the cantilever and measuring its response. In small amplitude approximation, where dither amplitude is comparable to persistence length of polymers, it is possible to measure the proteins viscoelastic response accurately. We measured dissipation in I27 at extremely low pulling speeds ([~] 50 nm/s) and low dither frequencies ([~]100 Hz). At these experimental parameters the dissipation is found to be [~]10-5 kg/s, well above the detection limit of conventional AFM and upper limit predicted by Benedetti et al. Our stiffness data clearly reveals unfolding intermediate of titins individual immunoglobulin units. The intermediate is elongation of folded domains by [~]8 [A], wherein two hydrogen bonds are broken between beta sheets. It was possible to measure this elongation in our experiments. The directly measured internal friction of unfolded polymer chain shows a scaling with tension on the chain. The measurements show that it is possible to measure internal friction in single molecules unambiguously using small amplitude AFM. It suggests that systematic experiments to unravel the relation between directly measured internal friction and folding rates of proteins are possible.

biophysics↗