Computational Chemistry Commons^™

Computational Insights Into Nucleosome Dynamics In Epigenetics Using Molecular Dynamics Simulations, Rutika Patel

Dissertations, Theses, and Capstone Projects

Nucleosome core particles (NCP) are the building blocks that form a highly organized and compact chromatin structure. Nucleosomes package DNA in the nucleus of eukaryotic cells. The NCP consists of about 147 base pairs of DNA wrapped around the histone octamer, with 1.65 superhelical turns in a left-handed manner. The histone octamer is composed of two copies of H3, H4, H2A, and H2B. Together with histone H1 and linker DNA, they further assemble into a higher-order chromatin structure. The nucleosome complex is stabilized by electrostatic interactions between positively charged histone residues and the negatively charged DNA backbone. To effectively access …

Design And In Silico Modeling Of Heterocyclic-Based Xanthone Derivatives As Potential Anticancer Agents Through Tyrosine Kinase Inhibition, Yehezkiel Steven Kurniawan, Ervan Yudha, Nela Fatmasari, Radite Yogaswara, Harno Dwi Pranowo, Eti Nurwening Sholikhah, Jumina Jumina

Makara Journal of Science

Cancer is one of the deadliest diseases nowadays, and tyrosine kinase receptors play crucial roles in cancer cell survival, differentiation, proliferation, and migration. This study designed and developed a new inhibitor from heterocyclic-based xanthone derivatives to target two tyrosine kinase receptors, epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFR), through in silico screening. Eighteen heterocyclic-based xanthones were evaluated through molecular docking for both receptors. All heterocyclic-based xanthones gave the root mean square deviation (RMSD) value lower than 2.00 Å. Xanthone with isobenzothiazole substituent (iBzThio) was found as the most potent inhibitor with binding energies of -10.60 and …

Investigating The In Vitro Antimicrobial Potential And Comprehensive Computational Studies Of New Schiff Base Derivatives, Abrar Hussain, Shahzaib Akhter, Hammad Nasir, Khurram Shahzad, Muhammad Arfan, Sand Hyun Park

Chemistry & Biochemistry Faculty Publications

Antimicrobial resistance (AMR) is a growing global health threat driven by multidrug-resistant bacteria (Staphylococcus aureus, Pseudomonas aeruginosa), and fungi (Candida albicans, and C. parapsilosis). This study evaluated six novel Schiff base derivatives (HSB-1 to HSB-6) through integrated in vitro antimicrobial activity and comprehensive computational studies. In vitro disk diffusion assay demonstrated the largest zones of inhibition against S. aureus for HSB-6 and HSB-1 (15–17 mm), activity against P. aeruginosa for HSB-5 and HSB-6 (12 mm), and moderate antifungal activity for HSB-4 (8–11 mm). Molecular docking results correlated with the in vitro findings with the binding energy ΔG = −12.3 kcal/mol …

Quantitative Structure-Activity Relationship, Pharmacokinetics, Drug-Likeness, Toxicity, And Molecular Docking Studies Of 4-N-(Methyl)-4-Aminoquinoline Derivatives As Antimalarial Compounds, Muhamad Jalil Baari, Devi Hardiyanti

Makara Journal of Science

Antimalarial drug resistance has encouraged various innovations to develop novel drug compounds that are effective, feasible, and safe, adhering to health standards. One way to do that is by observing and predicting the biological activity of drug compounds using quantitative structure–activity relationship (QSAR) analysis. In this study, QSAR analysis was conducted on the 4-N-(methyl)-4-aminoquinoline derivatives, which effectively inhibit the growth of Plasmodium falciparum as a source of malaria. The research stages involved molecular structure modeling, molecular geometry optimization using the AM1 semi-empirical method, and QSAR descriptor calculations, including electronic (atomic charges (q), HOMO and LUMO energies, polarizability (α), …

Exploration Of Euclidean Distances In Five-Dimensional Color Space As Proof-Of-Concept For Identification Of Promising Alternatives To Platinum-Based Cancer Drug Candidates, Kiomi Tanakura, Elena G. Harvey

Student Scholar Symposium

Cisplatin, cis-Pt(NH₃)₂Cl₂, is one of the most successful anticancer drugs of all time. However, it has some negative aspects, including toxicity to healthy cells, side effects, and cost. Our goal in this project is to design metal-based anticancer drugs that would be less expensive, less toxic, and more efficient for cancer patients than cisplatin. To begin this research we calculated Euclidean distances - as used by computerized recognition systems - to compare the properties of colors within seasonal palettes that are proven and visible to the eye. These Euclidean distances were then used …

Allosteric Control Overcomes Steric Limitations For Neutralizing Antibodies Targeting Conserved Binding Epitopes Of The Sars-Cov-2 Spike Protein: Exploring The Intersection Of Binding, Allostery, And Immune Escape With A Multimodal Computational Approach, Mohammed Alshahrani, Vedant Parikh, Brandon Foley, Gennady M. Verkhivker

Mathematics, Physics, and Computer Science Faculty Articles and Research

Understanding the atomistic basis of multi-layer mechanisms employed by broadly reactive neutralizing antibodies of the SARS-CoV-2 spike protein without directly blocking receptor engagement remains an important challenge in coronavirus immunology. Class 4 antibodies represent an intriguing case: they target a deeply conserved, cryptic epitope on the receptor-binding domain yet exhibit variable neutralization potency across subgroups F1 (CR3022, EY6A, COVA1-16), F2 (DH1047), and F3 (S2X259). The molecular basis for this variability is not fully understood. Here, we employed a multi-modal computational approach integrating atomistic and coarse-grained molecular dynamics simulations, binding free energy calculations, mutational scanning, and dynamic network analysis to elucidate …

Ensemble-Based Binding Free Energy Profiling And Network Analysis Of The Kras Interactions With Darpin Proteins Targeting Distinct Binding Sites: Revealing Molecular Determinants And Universal Architecture Of Regulatory Hotspots And Allosteric Binding, Mohammed Alshahrani, Vedant Parikh, Brandon Foley, Gennady M. Verkhivker

Mathematics, Physics, and Computer Science Faculty Articles and Research

KRAS is a pivotal oncoprotein that regulates cell proliferation and survival through interactions with downstream effectors such as RAF1. Despite significant advances in understanding KRAS biology, the structural and dynamic mechanisms of KRAS allostery remain poorly understood. In this study, we employ microsecond molecular dynamics simulations, mutational scanning, and binding free energy calculations together with dynamic network modeling to dissect how engineered DARPin proteins K27, K55, K13, and K19 engage KRAS through diverse molecular mechanisms ranging from effector mimicry to conformational restriction and allosteric modulation. Mutational scanning across all four DARPin systems identifies a core set of evolutionarily constrained residues …

Molecular Insights Into The Role Of Estrogen Receptor Beta In Ecdysterone Mediated Anabolic Activity, Syeda Sumayya Tariq, Madiha Sardar, Muhammad Shafiq, Hendrick Heinz, Mohammad Nur-E-Alam, Aftab Ahmad, Zaheer Ul-Haq

Pharmacy Faculty Articles and Research

Ecdysterone, often dubbed a “natural steroid,” has garnered significant attention among athletes for its reputed growth-promoting and anabolic properties. Unlike synthetic anabolic steroids, which are classified as controlled substances, ecdysteroids remain largely unregulated in many countries and are widely marketed as dietary supplements. Notably, ecdysterone has been included in the World Anti-Doping Agency (WADA) monitoring program, highlighting its potential impact on athletic performance and raising questions about its regulation. Emerging evidence indicates that, unlike traditional anabolic steroids that act primarily via the Androgen Receptor (AR), ecdysterone’s anabolic effects may be mediated through Estrogen Receptors (ERs), particularly Estrogen Receptor beta (ERβ). …

Towards Developing Glut2 Specific Probes For Biochemical And Biomedical Applications, Abdelrahman Ismail

Dissertations, Master's Theses and Master's Reports

Facilitated Glucose transporters (GLUTs) are membrane proteins responsible for the uptake of simple sugars and other structurally similar metabolites in all mammalian cells. One of the hallmarks of cancer is dysfunctional sugar metabolism, known as the Warburg effect, and one of the manifestations of that effect is abnormal GLUT expression. There are 14 known GLUT proteins with different expression patterns in different tissues, and tumors tend to express certain GLUTs that are not present in surrounding healthy tissue. Therefore, selective targeting of GLUTs presents a potentially powerful tool for diagnostics and treatment of cancer and other diseases. This has been …

Rational Design Of Small Molecules Targeting Mitochondrial Redox Proteins, Matheus Barbosa Belchior

Graduate Theses, Dissertations, and Problem Reports (ETD)

Reactive oxygen species play a crucial role in many cellular processes. Despite being a natural byproduct of cellular metabolism, overexpression of these species causes damage to the cell, leading to cell dysfunction. Central to the regulation of these highly reactive molecule is the mitochondria. Impairment in its function has been associated with oxidative stress within the cell. Herein, a ligand-based and structure-based approach to design new small molecules to inhibit mitochondrial redox proteins associated with oxidative stress and reactive oxygen species. In the first project two molecules were synthesized and characterized as potential monoamine oxidase B inhibitors. Results showed two …

Assembly Of Ppsu-Oligomers, Mariam Nesterov

Student Theses and Dissertations

The development of nanostructures for delivering multiple proteins to targeted antibodies has become a promising avenue in biotechnology, driven by advancements in synthetic polymers like poly(propylene sulfone), PPSU. However, the PPSU polymer faces a major limitation - its high insolubility. To address this challenge, this study investigates whether PPSU oligomers can enhance both the solubility and stability of lysozyme, a model protein that is cost-effective and widely accessible. Using dimer, trimer, tetramer, and hexamer configurations, we analyzed the interactions between PPSU oligomer and lysozyme under varying conditions. Our results show that the dimer and trimer are water soluble (no aggregate …

Computational Logp Calculations And Determination Of Lipophilicity Values Of Fluorinated Morphine Derivatives, Mirabella Romano, Allison Vu, Emily Chen

Student Scholar Symposium Abstracts and Posters

The addictive effect of opioids impacted 60 million people globally in 2023. This opioid crisis necessitates the development of opioid derivatives that maintain analgesic efficacy while minimizing addictive effects from opioid use. The present work focuses on morphine, a commonly prescribed opioid with high affinity to the mu-opioid receptor (MOR). Morphine binds non-selectively within both healthy and inflamed tissue. By modifying morphine’s structure through fluorination to counteract its non-selective binding, the drug’s pharmacological ability to provide effective pain relief comes with a lower risk of addiction. Specifically, the addition of fluorine to differing beta positions of the main binding site …

Incorporating Solvation Thermodynamic Mapping In Computer-Aided Drug Design, Yeonji Ji

Dissertations, Theses, and Capstone Projects

Advancements in computational techniques have revolutionized structure-based drug design, substantially improving the efficiency and effectiveness of the drug discovery process by reducing time, costs, and labor requirements. These advancements include various methods, such as investigating small molecule ligands binding to proteins, exploring alternative protein conformations, and solvation mapping on the protein surfaces. Among these methods, understanding the correlation between protein-ligand binding and the role of solvation is important.

A fundamental concept in protein-ligand binding is shape and electrostatic complementarity, which is complicated by the inherent flexibility of proteins. In the absence of small molecule ligands, proteins are complementary to surface …

Response To Replication Stress And Maintenance Of Genome Stability By Wrn, The Werner Syndrome Protein, David K. Orren, Amrita Machwe

Markey Cancer Center Faculty Publications

Werner syndrome (WS) is an autosomal recessive disease caused by loss of function of WRN. WS is a segmental progeroid disease and shows early onset or increased frequency of many characteristics of normal aging. WRN possesses helicase, annealing, strand exchange, and exonuclease activities and acts on a variety of DNA substrates, even complex replication and re- combination intermediates. Here, we review the genetics, biochemistry, and probably physiological functions of the WRN protein. Although its precise role is unclear, evidence suggests WRN plays a role in pathways that respond to replication stress and maintain genome stability particularly in telomeric regions.

Inchi Isotopologue And Isotopomer Specifications, Hunter N. B. Moseley, Philippe Rocca-Serra, Reza M. Salek, Masanori Arita, Emma L. Schymanski

Markey Cancer Center Faculty Publications

This work presents a proposed extension to the International Union of Pure and Applied Chemistry (IUPAC) International Chemical Identifier (InChI) standard that allows the representation of isotopically‑resolved chemi‑ cal entities at varying levels of ambiguity in isotope location. This extension includes an improved interpretation of the current isotopic layer within the InChI standard and a new isotopologue layer specification for representing chemical intensities with ambiguous isotope localization. Both improvements support the unique isotopically‑ resolved chemical identification of features detected and measured in analytical instrumentation, specifically nuclear magnetic resonance and mass spectrometry.

Scientific contribution

This new extension to the InChI standard …

Modeling Sex-Specific Changes In Myocardial Fibrosis, Grace Martin

Chemical Engineering Undergraduate Honors Theses

Heart disease the leading cause of death for both men and women in the United States. Cardiac fibrosis, or accumulation of extracellular matrix proteins in the heart, can occur after a heart attack and increase the risk for further complications. Current treatments for heart disease do not include extracellular matrix regulators, partly due to the complicated signaling network responsible for the production of these proteins. By using a computational model of the signaling network in cardia fibroblasts, the relationship between particular molecules and downstream extracellular matrix production can be examined.

Biological sex is an important factor for cardiac health and …

Accurate Characterization Of Binding Kinetics And Allosteric Mechanisms For The Hsp90 Chaperone Inhibitors Using Ai-Augmented Integrative Biophysical Studies, Chao Xu, Xianglei Zhang, Lianghao Zhao, Gennady M. Verkhivker, Fang Bai

Mathematics, Physics, and Computer Science Faculty Articles and Research

The binding kinetics of drugs to their targets are gradually being recognized as a crucial indicator of the efficacy of drugs in vivo, leading to the development of various computational methods for predicting the binding kinetics in recent years. However, compared with the prediction of binding affinity, the underlying structure and dynamic determinants of binding kinetics are more complicated. Efficient and accurate methods for predicting binding kinetics are still lacking. In this study, quantitative structure–kinetics relationship (QSKR) models were developed using 132 inhibitors targeting the ATP binding domain of heat shock protein 90α (HSP90α) to predict the dissociation rate …

In Silico Analysis Of C-Type Lectins As Co-Infection Receptors Of Dengue And Chikungunya Viruses In Aedes Aegypti, Munawir Sazali, R. C. Hidayat Soesilohadi, Nastiti Wijayanti, Tri Wibawa, Arif Nur Muhammad Ansori

Makara Journal of Science

Aedes aegypti is a primer vector of dengue virus (DENV) and chikungunya virus (CHIKV). The susceptibility of mosquitoes to DENV and CHIKV depends on their recognition receptor of pathogens. C-type lectins (CTLs) are an important mediator of virus infection in A. aegypti. This study aims to identify potential receptors and determine the binding affinity between ligand–receptor interaction, CTLs and virus envelopes (DENV-1, 2, 3, and 4 and CHIKV) interaction based on in silico analysis. Sample sequences were obtained from GenBank (NCBI), and 10 CTLs were acquired from VectorBase. Homology modeling based on a minimum standard of 20% was processed …

Mechanistic Investigation Of C—C Bond Activation Of Phosphaalkynes With Pt(0) Complexes, Roberto M. Escobar, Abdurrahman C. Ateşin, Christian Müller, William D. Jones, Tülay Ateşin

Research Symposium

Carbon–carbon (C–C) bond activation has gained increased attention as a direct method for the synthesis of pharmaceuticals. Due to the thermodynamic stability and kinetic inaccessibility of the C–C bonds, however, activation of C–C bonds by homogeneous transition-metal catalysts under mild homogeneous conditions is still a challenge. Most of the systems in which the activation occurs either have aromatization or relief of ring strain as the primary driving force. The activation of unstrained C–C bonds of phosphaalkynes does not have this advantage. This study employs Density Functional Theory (DFT) calculations to elucidate Pt(0)-mediated C–CP bond activation mechanisms in phosphaalkynes. Investigating the …

Β-Sheets Mediate The Conformational Change And Allosteric Signal Transmission Between The Aslov2 Termini, Sian Xiao, Mayar Terek Ibrahim, Gennady M. Verkhivker, Brian D. Zoltowski, Peng Tao

Mathematics, Physics, and Computer Science Faculty Articles and Research

Avena sativa phototropin 1 light-oxygen-voltage 2 domain (AsLOV2) is a model protein of Per-Arnt-Sim (PAS) superfamily, characterized by conformational changes in response to external environmental stimuli. This conformational change begins with the unfolding of the N-terminal A'α helix in the dark state followed by the unfolding of the C-terminal Jα helix. The light state is characterized by the unfolded termini and the subsequent modifications in hydrogen bond patterns. In this photoreceptor, β-sheets are identified as crucial components for mediating allosteric signal transmission between the two termini. Through combined experimental and computational investigations, the Hβ …

De Novo Drug Design Using Transformer-Based Machine Translation And Reinforcement Learning Of An Adaptive Monte Carlo Tree Search, Dony Ang, Cyril Rakovski, Hagop S. Atamian

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The discovery of novel therapeutic compounds through de novo drug design represents a critical challenge in the field of pharmaceutical research. Traditional drug discovery approaches are often resource intensive and time consuming, leading researchers to explore innovative methods that harness the power of deep learning and reinforcement learning techniques. Here, we introduce a novel drug design approach called drugAI that leverages the Encoder–Decoder Transformer architecture in tandem with Reinforcement Learning via a Monte Carlo Tree Search (RL-MCTS) to expedite the process of drug discovery while ensuring the production of valid small molecules with drug-like characteristics and strong binding affinities towards …

Spiral Wave Teleportation And Multiplex Network Synchronization In Light Sensitive Belousov-Zhabotinsky Systems, Shannyn Alicia Tyler

Graduate Theses, Dissertations, and Problem Reports (ETD)

We experimentally and computationally investigate dynamical behaviors in excitable and oscillatory media using light sensitive Belousov-Zhabotinsky (BZ) systems. These systems are not in a state of thermodynamic equilibrium, and have been proven to show various interesting phenomena including spatiotemporal patterns, self-organization, and chaos. We utilize the BZ reaction, a nonlinear chemical reaction, known for its relaxation-type oscillations, to explore the dynamics of these systems.

We examine spiral wave teleportation in an excitable media as an effective alternate defibrillation method. Spiral waves have emerged as a key phenomenon associated with the initiation and persistence of cardiac arrhythmias. Using a light sensitive …

Computational And Experimental Investigation Of Elemental Sulfur And Polysulfide, Jyoti Sharma

Dissertations

Petroleum processing results in the generation of significant quantities of elemental sulfur (S₈), leading to a surplus of sulfur worldwide. Despite its abundance and low cost, the use of sulfur in value-added organic compound synthesis is limited due to its unpredictable and misunderstood reactivity. This dissertation aims to address this issue by tackling it from two angles. Firstly, by utilizing Density Functional Theory (DFT) calculations, the reactivity of sulfur in the presence of nucleophiles is studied. This facilitates the identification of organic polysulfide intermediates that can be generated under different conditions, as well as the corresponding reactivity for …

Atomistic Assessment Of Drug-Phospholipid Interactions Consequent To Cancer Treatment: A Study Of Anthracycline Cardiotoxicity, Yara Elsayed Ahmed

Theses and Dissertations

Despite being one of the most effective chemotherapeutic agents developed to date, Anthracyclines are notorious for their cardiotoxicity. Their clinical use is frequently limited both in dosage and in prescription due to the severe cardiac damage they cause. The mechanism of anthracycline-induced cardiotoxicity is not yet fully understood. However, it is hypothesized that interactions with the myocardial membrane play an important role in imparting cardiotoxicity. In this study, we use molecular dynamics simulations and density functional theory calculations to study the anthracycline drug molecules and the interactions that they have with the myocardial membrane. We construct a myocardial membrane model …

Chatgpt As Metamorphosis Designer For The Future Of Artificial Intelligence (Ai): A Conceptual Investigation, Amarjit Kumar Singh (Library Assistant), Dr. Pankaj Mathur (Deputy Librarian)

Library Philosophy and Practice (e-journal)

Abstract

Purpose: The purpose of this research paper is to explore ChatGPT’s potential as an innovative designer tool for the future development of artificial intelligence. Specifically, this conceptual investigation aims to analyze ChatGPT’s capabilities as a tool for designing and developing near about human intelligent systems for futuristic used and developed in the field of Artificial Intelligence (AI). Also with the helps of this paper, researchers are analyzed the strengths and weaknesses of ChatGPT as a tool, and identify possible areas for improvement in its development and implementation. This investigation focused on the various features and functions of ChatGPT that …

Probing Mechanisms Of Binding And Allostery In The Sars-Cov-2 Spike Omicron Variant Complexes With The Host Receptor: Revealing Functional Roles Of The Binding Hotspots In Mediating Epistatic Effects And Communication With Allosteric Pockets, Gennady M. Verkhivker, Steve Agajanian, Ryan Kassab, Keerthi Krishnan

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this study, we performed all-atom MD simulations of RBD–ACE2 complexes for BA.1, BA.1.1, BA.2, and BA.3 Omicron subvariants, conducted a systematic mutational scanning of the RBD–ACE2 binding interfaces and analysis of electrostatic effects. The binding free energy computations of the Omicron RBD–ACE2 complexes and comprehensive examination of the electrostatic interactions quantify the driving forces of binding and provide new insights into energetic mechanisms underlying evolutionary differences between Omicron variants. A systematic mutational scanning of the RBD residues determines the protein stability centers and binding energy hotpots in the Omicron RBD–ACE2 complexes. By employing the ensemble-based global network analysis, we …

Interpretable Machine Learning Models For Molecular Design Of Tyrosine Kinase Inhibitors Using Variational Autoencoders And Perturbation-Based Approach Of Chemical Space Exploration, Keerthi Krishnan, Ryan Kassab, Steve Agajanian, Gennady M. Verkhivker

Mathematics, Physics, and Computer Science Faculty Articles and Research

In the current study, we introduce an integrative machine learning strategy for the autonomous molecular design of protein kinase inhibitors using variational autoencoders and a novel cluster-based perturbation approach for exploration of the chemical latent space. The proposed strategy combines autoencoder-based embedding of small molecules with a cluster-based perturbation approach for efficient navigation of the latent space and a feature-based kinase inhibition likelihood classifier that guides optimization of the molecular properties and targeted molecular design. In the proposed generative approach, molecules sharing similar structures tend to cluster in the latent space, and interpolating between two molecules in the latent space …

A Proposed Treatment Of Mixed Connective Tissue Disease By Competitive Inhibition Of Autoantibodies, Thomas Russell

Senior Honors Theses

Mixed Connective Tissue Disease is an autoimmune disease characterized by Raynaud’s phenomenon and arthritis among other symptoms. It is primarily caused by antibodies that target the U1-RNP 70K peptide. The treatment proposed in this paper uses competitive inhibition to prevent the binding of the anti-U1-RNP 70K antibodies with the U1-RNP 70K peptide. A method for testing the designed treatment in silico is proposed using AutoDock Vina docking software.

Development Of Accurate And Efficient Computational Methodologies For Predicting Protein-Ligand And Protein-Protein Binding Free Energies, Alexander Hamilton Williams

Theses and Dissertations--Pharmacy

Computational modeling is an invaluable tool in the drug discovery process either for small ligand or protein therapeutics. The widespread availability of protein X-Ray Crystal and Cryo-Electron Microscopy (Cryo-EM) structures has allowed for more accurate molecular dynamics (MD) simulations that are not reliant on methods such as homology modeling, which may produce structures that require significant computational time to demonstrate their stability. In this thesis we describe several novel methodologies for the computationally efficient modeling of protein/ligand and protein/protein complexes that may be employed within both large-scale virtual screenings and lead compound optimization. These methodologies may also be utilized in …

Fluorescence Spectroscopic And Molecular Modelling Studies On The Molecular Interaction Mechanism Of Bromodeoxyuridine With Human Serum Albumin, Amira Adlin Roslan

Student Works (2020-2029)

The interaction of a nucleoside analogue, bromodeoxyuridine (BrdU) with human serum albumin (HSA) was studied to investigate the binding phenomenon and analyze the protein conformation upon BrdU binding. Multiple spectroscopic techniques, viz. intrinsic and three-dimensional (3-D) fluorescence, ultraviolet-visible (UV-Vis) absorption and circular dichroism (CD) spectroscopy along with molecular docking were used. A decrease in the Stern-Volmer constant (Ksv) with the increase in temperature suggested BrdU-induced quenching of protein fluorescence as static quenching and thus implied BrdU−HSA complex formation. This was also supported by UV-Vis absorption spectral results, showing hyperchromism in the absorption spectrum of HSA upon BrdU addition. Intermediate binding …