Multi-component redox system for selective and potent antineoplastic activity towards ovarian cancer cells.

Ovarian cancer is the deadliest gynecological cancer which rarely causes symptoms, and goes undetected until reaching the advanced stage of drug-resistant metastases. The cationic porphyrin meso-tetra(4-N-methylpyridyl)porphine (TMPyP) is a well-known photosensitizer (PS) used in photodyamic therapy (PDT) for curing cancer due to its strong affinity for DNA and high yield of reactive oxygen species (ROS) upon light activation. The practicality to irradiate tumor cells alone in the physiological system being slim (due to the close proximity of healthy cells and tumors), we looked for a variation in the PDT using a mixture of TMPyP with 1,5-dihydroxynapthalene (DHN) and Fe(III) ions at a mole ratio of 1:20:17 (drug combo) respectively in aqueous solution. The drug combo needs no photoactivation in H2O2 rich environment (mimicking the microenvironment of cancer/tumor), where it generates È®H and juglone, the latter being a known potent anticancer agent. In vitro studies of the drug combo in drug resistant and sensitive ovarian cancer cell lines showed drastic growth inhibition and cell death compared to normal epithelial cells. The drug combo provides an effective and non-invasive alternative to conventional PDT, exploiting the cytosolic carcinogenic H2O2 to produce an efficient anticancer treatment. The unique action of cancer-specific cytotoxicity arises from the redox chemistry involving activation of Fe(III) as the oxidizing agent to generate juglone, which utilizes the cytosolic ROS in cancer cells against itself.

Spectroscopic Study on Pseudomonas Aeruginosa Biofilm in the Presence of the Aptamer-DNA Scaffolded Silver Nanoclusters.

We report the effectiveness of silver nanocluster (Ag-NC) against the biofilm of Pseudomonas aeruginosa (PA). Two DNA aptamers specific for PA and part of their sequences were chosen as templates for growing the Ag-NC. While circular dichroism (CD) studies determined the presence of secondary structures, UV/Vis absorption, and fluorescence spectroscopic studies confirmed the formation of the fluorescent Ag-NC on the DNA templates. Furthermore, mesoscopic physics-based partial wave spectroscopy (PWS) was used to analyze the backscattered light signal that can detect the degree of nanoscale mass density/refractive index fluctuations to identify the biofilm formation, comparatively among the different aptamers with respect to the control sample. The importance of the secondary structure of the aptamer DNA in targeting, successfully binding with the cells and delivering the Ag-NC, is evidenced by the decrease in disorder strength (Ld) of the Ag-NC treated samples compared to the untreated PA cells, which showed the abundance of higher Ld in the PWS studies. The higher Ld value attributed to the higher mass density fluctuations and the formation of biofilm. We envision this study to open a new avenue in using a powerful optical microscopic technique like PWS in detection, and DNA aptamer enclosed silver nanoclusters to prevent biofilms for opportunist pathogens like Pseudomonas aeruginosa.

Optical sensing by transforming chromophoric silver clusters in DNA nanoreactors.

Bifunctional DNA oligonucleotides serve as templates for chromophoric silver clusters and as recognition sites for target DNA strands, and communication between these two components is the basis of an oligonucleotide sensor. Few-atom silver clusters exhibit distinct electronic spectra spanning the visible and near-infrared region, and they are selectively synthesized by varying the base sequence of the DNA template. In these studies, a 16-base cluster template is adjoined with a 12-base sequence complementary to the target analyte, and hybridization induces structural changes in the composite sensor that direct the conversion between two spectrally and stoichiometrically distinct clusters. Without its complement, the sensor strand selectively harbors ~7 Ag atoms that absorb at 400 nm and fold the DNA host. Upon association of the target with its recognition site, the sensor strand opens to expose the cluster template that has the binding site for ~11 Ag atoms, and absorption at 720 nm with relatively strong emission develops in lieu of the violet absorption. Variations in the length and composition of the recognition site and the cluster template indicate that these types of dual-component sensors provide a general platform for near-infrared-based detection of oligonucleotides in challenging biological environments.

Mechanistic insight into the structure and dynamics of entangled and hydrated λ-phage DNA.

Intrinsic dynamics of DNA plays a crucial role in DNA-protein interactions and has been emphasized as a possible key component for in vivo chromatin organization. We have prepared an entangled DNA microtube above the overlap concentration by exploiting the complementary cohesive ends of λ-phage DNA, which is confirmed by atomic force microscopy and agarose gel electrophoresis. Photon correlation spectroscopy further confirmed that the entangled solutions are found to exhibit the classical hydrodynamics of a single chain segment on length scales smaller than the hydrodynamic length scale of single λ-phage DNA molecule. We also observed that in 41.6% (gm water/gm DNA) hydrated state, λ-phage DNA exhibits a dynamic transition temperature (T(dt)) at 187 K and a crossover temperature (T(c)) at 246 K. Computational insight reveals that the observed structure and dynamics of entangled λ-phage DNA are distinctively different from the behavior of the corresponding unentangled DNA with open cohesive ends, which is reminiscent with our experimental observation.

A CRITICAL STUDY ON THE INTERACTIONS OF HESPERITIN WITH HUMAN HEMOGLOBIN: FLUORESCENCE SPECTROSCOPIC AND MOLECULAR MODELING APPROACH.

Hesperitin, a ubiquitous bioactive flavonoid abundant in citrus fruits is known to possess antioxidant, anti-carcinogenic, hypolipidemic, vasoprotective and other important therapeutic properties. Here we have explored the interactions of hesperitin with normal human hemoglobin (HbA), using steady state and time resolved fluorescence spectroscopy, far UV circular dicroism (CD) spectroscopy, combined with molecular modeling computations. Specific interaction of the flavonoid with HbA is confirmed from flavonoid-induced static quenching which is evident from steady state fluorescence as well as lifetime data. Both temperature dependent fluorescence measurements and molecular docking studies reveal that apart from hydrogen bonding and van der Waals interactions, electrostatic interactions also play crucial role in hesperitin-HbA interactions. Furthermore, electrostatic surface potential calculations indicate that the hesperitin binding site in HbA is intensely positive due to the presence of several lysine and histidine residues.

Anticancer Properties of Kaempferol on Cellular Signaling Pathways.

Polyhydroxy compounds are secondary metabolites that are ubiquitous in plants of higher genera. They possess therapeutic properties against a wide spectrum of diseases, including cancers, neurodegenerative disorders, atherosclerosis, as well as cardiovascular disease. The phytochemical flavonol (a type of flavonoid) kaempferol (KMP) (3,5,7-trihydroxy-2-(4-hydroxyphenyl)- 4Hchromen-4-one) is abundant in cruciferous vegetables, including broccoli, kale, spinach, and watercress, as well as in herbs like dill, chives, and tarragon. KMP is predominantly hydrophobic in nature due to its diphenylpropane structure (a characteristic feature of flavonoids). Recent findings have indicated the promise of applying KMP in disease prevention due to its potential antioxidant, antimutagenic, antifungal, and antiviral activities. In the literature, there is evidence that KMP exerts its anticancer effects by modulating critical elements in cellular signal transduction pathways linked to apoptosis, inflammation, angiogenesis, and metastasis in cancer cells without affecting the viability of normal cells. It has been shown that KMP triggers cancer cell death by several mechanisms, including cell cycle arrest, caspase activation, metabolic alteration, and impacting human telomerase reverse-transcriptase gene expression. This review is aimed at providing critical insights into the influence of KMP on the intracellular cascades that regulate metabolism and signaling in breast, ovarian, and cervical cancer cells.

DNA sensing by amplifying the number of near-infrared emitting, oligonucleotide-encapsulated silver clusters.

A bifunctional oligonucleotide integrates in situ synthesis of a fluorogenic silver cluster with recognition of a target DNA sequence. With the template C(3)AC(3)AC(3)GC(3)A, a complex forms with 10 silver atoms that possesses electronic transitions in the near-infrared and that is detected at nanomolar concentrations using diode laser excitation. Pendant to this cluster encoding region, the recognition component binds a target DNA strand through hybridization, and decoupling of these two regions of the composite sensor renders a modular sensor for specific oligonucleotides. A target is detected using a quencher strand that bridges the cluster template and recognition components and disturbs cluster binding, as indicated by static quenching. Competitive displacement of the quencher by the target strand restores the favored cluster environment, and our key finding is that this exchange enhances emission through a proportional increase in the number of emissive clusters. DNA detection is also accomplished in serum-containing buffers by taking advantage of the high brightness of this fluorophore and the inherently low endogenous background in the near-infrared spectral region. Cluster stability in this biological environment is enhanced by supplementing the solutions with Ag(+).

Transepithelial Anti-Neuroblastoma Response to Kale among Four Vegetable Juices Using In Vitro Model Co-Culture System.

Juicing vegetables is thought to be an anticancer treatment. Support exists for a rank order of anticancer greens (kale > dandelion > lettuce > spinach) based on degrees of bioavailability of different phytochemicals, also offset by some noxious molecules (i.e., calcium-oxalate). We developed a new in vitro transepithelial anti-neuroblastoma model system. The juices were diluted as predicted once in the small intestine. They were applied to apical Caco-2Bbe1 cells atop dividing SH-SY5Y neuroblastoma cells, and changes in transepithelial electrical resistance (TEER) and cell growth were considered with juice spectroscopies. Studied first in monoculture, kale and dandelion were the most cytostatic juices on SH-SY5Ys, lettuce showed no effect, and high (4.2%) spinach was cytotoxic. In co-culture, high (4.2%) kale was quickest (three days) to inhibit neuroblastoma growth. By five days, dandelion and kale were equally robust. Lettuce showed small anti-proliferative effects at five days and spinach remained cytotoxic. Spinach's cytotoxicity corresponded with major infrared bands indicative of oxalate. Kale juice uniquely induced reactive oxygen species and S-phase cell cycle arrest in SH-SY5Y. The superiority of kale and dandelion was also apparent on the epithelium, because raising TEER levels is considered healthy. Kale's unique features corresponded with a major fluorescent peak that co-eluted with kaempferol during high performance liquid chromatography. Because the anticancer rank order was upheld, the model appears validated for screening anticancer juices.

Health disparity and COVID-19-A retrospective analysis.

BACKGROUND AND AIMS: According to the World Health Organization (WHO), more than 75.7 million confirmed cases of coronavirus disease 2019 (COVID-19), a global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have been reported so far. Researchers are working relentlessly to find effective solutions to this catastrophe, using genomic sequence-based investigation, immunological analysis, and more. The role of health disparity has also emerged as an intriguing factor that made a huge impact on the lives of people. METHODS: We analyzed various factors that triggered the health disparity in the United States of America along with the rate of COVID-19 morbidity and mortality. Furthermore, we have also focused on the State of Mississippi, which is suffering from an extreme health disparity. Data have been obtained from publicly available data sources including, Center for Disease Control and Prevention and Mississippi State Department of Health. Correlation analysis of the dataset has been performed using R software. RESULTS: Our analysis suggested that the COVID-19 infection rate per 100 000 people is directly correlated with the increasing number of the African American population in the United States. We have found a strong correlation between the obesity and the COVID-19 cases as well. All the counties in Mississippi demonstrate a strong correlation between a higher number of African American population to COVID-19 cases and obesity. Our data also indicate that a higher number of African American populations are facing socioeconomic disadvantages, which enhance their chances of becoming vulnerable to pre-existing ailments such as obesity, type-2 diabetes, and cardiovascular diseases. CONCLUSION: We proposed a possible explanation of increased COVID-19 infectivity in the African American population in the United States. This work has highlighted the intriguing factors that increased the health disparity at the time of the COVID-19 pandemic.

Context dependence of trinucleotide repeat structures.

Long repeated sequences of DNA and their associated secondary structure govern the development and severity of a significant class of neurological diseases. Utilizing the effect of base stacking on fluorescence quantum yield, 2-aminopurine substitutions for adenine previously demonstrated sequestered bases in the stem and exposed bases in the loop for an isolated (CAG)(8) sequence. This study evaluates (CAG)(8) that is incorporated into a duplex, as this three-way junction is a relevant model for intermediates that lead to repeat expansion during DNA replication and repair. From an energetic perspective, thermally induced denaturation indicates that the duplex arms dictate stability and that the secondary structure of the repeated sequence is disrupted. Substitutions with 2-aminopurine probe base exposure throughout this structure, and two conclusions about secondary structure are derived. First, the central region of (CAG)(8) is more solvent-exposed than single-stranded DNA, which suggests that hairpin formation in the repeated sequence is disrupted. Second, base stacking becomes compromised in the transition from the duplex to (CAG)(8), resulting in bases that are most similar to single-stranded DNA at the junction. Thus, an open (CAG)(8) loop and exposed bases in the arms indicate that the strand junction profoundly influences repeated sequences within three-way junctions.

Structural studies of a trinucleotide repeat sequence using 2-aminopurine.

The secondary structure of repeated trinucleotide sequences results in the development of several neurodegenerative diseases, and these studies consider the (CAG)(8) sequence that forms a stem-loop hairpin. The structural and thermodynamic properties of this hairpin are assessed using 2-aminopurine substitutions for adenine at six positions in this repeated sequence. Circular dichroism spectra and thermal denaturation experiments show that the secondary structure is not disturbed by the modifications. The local structure of the hairpin was monitored using the fluorescence intensities of 2-aminopurines, the changes in the intensity relative to the denatured state, and the sensitivity of the fluorescence to quenching by acrylamide. To establish the stem and loop characteristics in (CAG)(8), known reference points for stem, loop, and exposed base motifs were used. In the vicinity of the loop, the bases become more solvent exposed, which suggests that the instability associated with this repeated hairpin influences the global secondary structure. These results provide the basis to interpret the structures adopted by other repeated (CAG) structures.

Graphene oxide as selective transporter of flavonols for physiological target DNA: A two-color fluorescence approach.

Our study determines the selectivity of graphene oxide (GO) to recognize its ligands (e.g. flavonoids) in facilitating the binding with their respective cellular targets. The polyhydroxy phenolic compounds, flavonoids, have a broad spectrum of therapeutic activities with high potency and low systemic toxicity. Despite the vast medicinal importance, their bioavailability is low. In this exploratory study, GO has been used as the transporter of three flavonols fisetin (3, 7, 3', 4'-OH flavone), quercetin (3, 5, 7, 3', 4'-OH flavone), and morin (3, 5, 7, 2', 4'-OH flavone) for the physiological target DNA. Calf thymus DNA is chosen as the model physiological target. Characterization of GO is performed using FTIR, Raman and dynamic light scattering (DLS) spectroscopy. The strong absorption peak at 1730 cm-1 indicated the presence of carbonyl groups (C=O) at the edges of GO. The presence of sp3 carbons due to oxidation of sp2 carbons in GO is further proved by Raman spectroscopy. DLS provided the average size of the GO particles to be ~9 µm. The dual luminescence behavior of the flavonols has been used in this study for the noninvasive sensing of the GO-flavonol and GO-flavonol-DNA interactions; as well as for the selectivity of GO for one flavonol over other in transferring the ligand to DNA. Furthermore, circular dichroism (CD) indicated that the optical activity of GO undergoes drastic change when conjugated with flavonols. Molecular modeling corroborated the findings from the binding studies. GO provides high promise as facilitators for drug delivery.

Differential roles of 3-Hydroxyflavone and 7-Hydroxyflavone against nicotine-induced oxidative stress in rat renal proximal tubule cells.

Plant flavonoids are well known as antioxidants against oxidative stress induced by exposure to external pollutants. Nicotine (NIC) is one of those agents which increases renal oxidative stress, an important factor in the pathogenesis of renal epithelial injury in smokers. Although several studies had been conducted on flavonoids and oxidative stress, the mechanism of the protective pathways are not fully understood. Here, we present studies on antioxidant properties of two mono-hydroxyflavone isomers, 3-hydroxyflanove (3HF)- and 7-hydroxyflavone (7HF), against nicotine-associated oxidative stress and injury in cultured renal proximal tubule cells and correlate their antioxidant properties with their chemical structure. Our data clearly demonstrates, for the first time, that while both 3HF and 7HF protect renal cells from NIC-associated cytotoxicity, the mechanism of their action is different: 3HF elicits protective activity via the PKA/CREB/MnSOD pathway while 7HF does so via the ERK/Nrf2/HO-1 pathway. Molecular docking and dynamics simulations with two major signaling pathway proteins showed significant differences in the binding energies of 3HF (-5.67 and -7.39 kcal.mol-1) compared to 7HF (-5.41 and -8.55 kcal.mol-1) in the matrices of CREB and Keap1-Nrf2 proteins respectively, which corroborate with the observed differences in their protective properties in the renal cells. The implications of this novel explorative study is likely to promote the understanding of the mechanisms of the antioxidative functions of different flavones.

Chiral alkylated-aniline as a noninvasive fluorescence sensor: Spectroscopic and molecular modeling studies.

Aniline, heterocyclic aromatic amines, and arylamines are known carcinogens. Recently aniline mustard has come into prominence as a novel anticancer agent. In this project, microwave irradiation has been used to synthesize an optically active alkylated aniline namely 2,6-dimethyl-4-(1-(p-tolyl)ethyl)aniline (abbreviated DMPA). The presence of quartet and doublet peaks in NMR and a single chromatogram in HPLC verified that the final product DMPA, prepared from the synthesis reactions, had no major impurities. By using a Lux chiral column in HPLC, two peaks have been detected in the chromatogram, which correspond to two enantiomers of the chiral aniline derivative. Fluorescence spectroscopic measurements on DMPA indicated conspicuous dependence of its emission behavior on the polarity (in terms of the empirical polarity parameter ET(30)) of the homogeneous solvents used, a property important for an optical sensor. The nature of the emission profiles, along with the relevant parameter namely wavelength at emission maximum (λemmax) is used to infer the distribution, binding and microenvironment of the DMPA molecules in human serum albumin protein (HSA). DMPA is weakly fluorescent in aqueous buffer medium, with a dramatic enhancement in the fluorescence emission in the presence of HSA. Molecular modeling studies have been carried out on the two enantiomers (R and S) of DMPA with HSA. The implications of these findings are examined in relation to the potentialities of DMPA as a novel fluorescence sensor for biological systems.

Excited state proton transfer of natural flavonoids and their chromophores in duplex and tetraplex DNAs.

Fisetin (3,7,3',4'-tetrahydroxyflavone) and quercetin (3,5,7,3',4'-pentahydroxyflavone) are the bioactive plant flavonoids that are potentially useful therapeutic drugs for the treatment of a broad spectrum of diseases, including atherosclerosis, cardiovascular disease, obesity, hypertension, and cancer. 3-Hydroxyflavone (3HF) and 7-hydroxyflavone (7HF) are the synthetic chromophores of fisetin and quercetin. We have exploited dual luminescence properties of fisetin and quercetin along with 3-HF and 7HF to examine their efficacy of binding and compare their interactions with DNA, which is one of the macromolecular targets of flavonoids in physiological systems. Following the sequence of the human telomeric DNA 5'-d (CCCTAA-)n/(-TTAGGG)n-5', two single-stranded DNA oligonucleotides, 5'-d(C3TA2)3C3-3' and 5'-d(T2AG3)4-3', and their duplex were used as receptors to study binding by the ligands quercetin, fisetin, and their chromophores. Circular dichroism, differential absorption, UV thermal melting, and size exclusion chromatographic studies indicated the formation of unusual DNA structures (such as C4 and G4 tetraplexes) for both the C- and G-rich single-stranded DNAs. Upon binding to DNA, dramatic changes were observed in the intrinsic fluorescence behavior of the flavonoids. Molecular docking studies were performed to describe the likely binding sites for the ligands. The spectroscopic studies on flavonoid-DNA interactions described herein demonstrate a powerful approach for examining their DNA binding through exploiting the highly sensitive intrinsic fluorescence properties of the flavonoids as their own "reporter" for their interactions with macromolecular targets.

Prospect of bioflavonoid fisetin as a quadruplex DNA ligand: a biophysical approach.

Quadruplex (G4) forming sequences in telomeric DNA and c-myc promoter regions of human DNA are associated with tumorogenesis. Ligands that can facilitate or stabilize the formation and increase the stabilization of G4 can prevent tumor cell proliferation and have been regarded as potential anti-cancer drugs. In the present study, steady state and time-resolved fluorescence measurements provide important structural and dynamical insights into the free and bound states of the therapeutically potent plant flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) in a G4 DNA matrix. The excited state intra-molecular proton transfer (ESPT) of fisetin plays an important role in observing and understanding the binding of fisetin with the G4 DNA. Differential absorption spectra, thermal melting, and circular dichroism spectroscopic studies provide evidences for the formation of G4 DNA and size exclusion chromatography (SEC) proves the binding and 1∶1 stoichiometry of fisetin in the DNA matrix. Comparative analysis of binding in the presence of EtBr proves that fisetin favors binding at the face of the G-quartet, mostly along the diagonal loop. Time resolved fluorescence anisotropy decay analysis indicates the increase in the restrictions in motion from the free to bound fisetin. We have also investigated the fingerprints of the binding of fisetin in the antiparallel quadruplex using Raman spectroscopy. Preliminary results indicate fisetin to be a prospective candidate as a G4 ligand.

Interactions of dietary flavonoids with proteins: insights from fluorescence spectroscopy and other related biophysical studies.

In 1936, Rusznyak and Szent-Györgyi first drew attention to the therapeutically beneficial role of dietary flavonoids, which are the most common group of polyphenols ubiquitously present in plant based food and beverages. Recent years have witnessed a renascence of interest on these nutraceuticals, which, because of their high potency and low systemic toxicity, are gradually emerging as promising alternatives to conventional therapeutic drugs. There is a mounting evidence that various proteins frequently serve as targets for therapeutically important flavonoids. In this article we present perspectives exemplifying the growing potential of fluorescence spectroscopy as an exquisitely sensitive tool for noninvasive sensing of protein-flavonoid interactions at physiologically relevant concentrations, via measurements of steady state emission parameters as well as decay kinetics studies of the intrinsic fluorescence of the target (protein) and/or ligand (flavonoid). Especially, we highlight novel applications of the remarkably environment sensitive 'two color' fluorescence exhibited by many important flavonoids, which permits multiparametric and ratiometric measurements. To consolidate findings obtained via fluorescence spectroscopy, use of other relevant experimental biophysical techniques and molecular modeling have proved to be valuable and are also discussed here. Such complementary studies provide additional insights regarding the thermodynamics and conformational aspects of the protein-flavonoid interactions, together with details, at atomistic level, of the dominant noncovalent interactions involved in the docking of different flavonoids to their target proteins.

Contrasting binding of fisetin and daidzein in γ-cyclodextrin nanocavity.

Steady state and time resolved fluorescence along with anisotropy and induced circular dichroism (ICD) spectroscopy provide useful tools to observe and understand the behavior of the therapeutically important plant flavonoids fisetin and daidzein in γ-cyclodextrin (γ-CDx) nanocavity. Benesi-Hildebrand plots indicated 1:1 stoichiometry for both the supramolecular complexes. However, the mode of the binding of fisetin significantly differs from daidzein in γ-CDx, as is observed from ICD spectra which is further confirmed by docking studies. The interaction with γ-CDx proceeds mainly by the phenyl ring and partly by the chromone ring of fisetin whereas only the phenyl ring takes part for daidzein. A linear increase in the aqueous solubility of the flavonoids is assessed from the increase in the binding of the flavonoids with the γ-CDx cavity, which are determined by the gradual increase in the ICD signal, fluorescence emission as well as increase in fluorescence anisotropy with increasing (γ-CDx). This confirms γ-CDx as a nanovehicle for the flavonoids fisetin and daidzein in improving their bioavailability.

Binding and antioxidant properties of therapeutically important plant flavonoids in biomembranes: insights from spectroscopic and quantum chemical studies.

Plant flavonoids are emerging as novel therapeutic drugs for free radical mediated diseases, for which cell membranes mainly serve as targets for lipid peroxidation and related deleterious effects. Screening and characterization of these ubiquitous, therapeutically potent polyphenolic compounds require a clear understanding regarding their binding and possible locations in membranes, as well as quantitative estimates of relevant parameters such as partition coefficients, antioxidant and radical scavenging capacities. In this article we present perspectives emphasizing novel uses of the exquisitely sensitive 'two color' intrinsic fluorescence of plant flavonoids (which arise due to highly efficient photoinduced excited state intramolecular proton transfer (ESIPT) reactions) to explore their binding to model biomembranes consisting of phosphatidylcholine liposomes. Extension of such studies to natural biomembranes of relevant interest is also exemplified. Spectrophotometric assays reveal that typical mono- as well as poly-hydroxy substituted flavonoids have remarkable inhibitory actions on lipid peroxidation, and are significantly more potent antioxidants (2.5-4 times higher) compared to the reference compound Trolox (an water soluble derivative of vitamin E). The structure-activity relationships emerging from such studies are consistent with theoretical predictions based on quantum chemical computations.

Characterization of diadzein-hemoglobin binding using optical spectroscopy and molecular dynamics simulations.

The present study establishes the effectiveness of natural drug delivery mechanisms and investigates the interactions between drug and its natural carrier. The binding between the isoflavone diadzein (DZN) and the natural carrier hemoglobin (HbA) was studied using optical spectroscopy and molecular dynamics simulations. The inherent fluorescence emission characteristics of DZN along with that of tryptophan (Trp) residues of the protein HbA were exploited to elucidate the binding location and other relevant parameters of the drug inside its delivery vehicle HbA. Stern-Volmer studies at different temperatures indicate that static along with collisional quenching mechanisms are responsible for the quenching of protein fluorescence by the drug. Molecular dynamics and docking studies supported the hydrophobic interactions between ligand and protein, as was observed from spectroscopy. DZN binds between the subunits of HbA, ∼15 Å away from the closest heme group of chain α1, emphasizing the fact that the drug does not interfere with oxygen binding site of HbA.