Photochromic Receptors for Nucleotide Detection using Machine Learning Techniques

Sahanawaz, Md. (2026) Photochromic Receptors for Nucleotide Detection using Machine Learning Techniques. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Md Sahanawaz (18RS036)) 18RS036.pdf - Submitted Version Restricted to Repository staff only Download (48MB)

Abstract

Multianalyte discrimination of structurally similar nucleotide phosphates remains a persistent challenge for conventional supramolecular sensors, which typically rely on a single binding mode and produce one-dimensional responses. In this thesis, an azobenzene-based tripodal photoswitch is developed as a light-addressable receptor that undergoes reversible cis–trans isomerization, with each isomer exhibiting distinct recognition behaviour toward nucleotide phosphates and inorganic phosphate. The two photoaccessible states display markedly different binding affinities and interaction patterns with biologically relevant nucleotides including ATP, ADP, GTP, UMP, UTP, and CTP. By modulating the receptor configuration using UV and visible light, a single molecular system effectively generates multiple sensing outputs, allowing each isomer to function as an independent sensing element. Receptor–analyte interactions were monitored using UV–visible spectroscopy, and the resulting high-dimensional spectral responses were analysed using supervised multivariate techniques, specifically Linear Discriminant Analysis. This approach enabled reliable discrimination and classification of multiple nucleotide species from overlapping spectral data, demonstrating that photoisomerization can be exploited to introduce orthogonal sensing dimensions within a single receptor framework. In parallel, the influence of polymer microenvironment on photoresponsive behaviour was investigated using azobenzene-containing copolymers bearing stearate side chains with controlled monomer sequences. Variations in polymer architecture and local polarity were found to significantly modulate the thermal cis–trans isomerization kinetics by stabilizing or destabilizing the isomerization transition state, thereby tuning the cis-isomer lifetime. Collectively, this work establishes a strategy for combining photoswitchable supramolecular recognition with multivariate analysis and sequence-defined polymer design to create environmentally responsive photochromic sensing materials.

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