BIOMACROMOLECULAR JOURNAL
Year:2015 | Volume:1 | Issue:2|Papers Count:11

Hemoglobin is a tetrameric oxygen transport protein in animal bodies. However, there is a paucity of information regarding differences between alpha and beta subunits of hemoglobin in terms of oxygen affinity. The sequential model of Koshland, Nemthy and Filmer (KNF model) has attributed similar affinities to both alpha and beta subunits. The main purpose of the present study is to construct a new sequential model for hemoglobin oxygenation based on higher oxygen affinities for alpha subunits. To this end, coordinate files of 19 oxy and 41 deoxy hemoglobin structures were used as starting structures. These files were processed using Microsoft Excel and SPSS software in order to calculate Euclidean distances between each pair of proximal and distal histidine Fe2+ as well as other pairs of atoms of interest. The calculated distances were then compared for either set of hemoglobin conformations, i.e. oxy and deoxy conformations. Our results showed that a2 subunit show higher structural changes that could be related to oxygen affinity. This subunit could be introduced as initiator of hemoglobin oxygenation and cooperativity. Subunit a2 in our sequential model induces relaxed conformation in a1, b2 and b1 respectively. The order of oxygen affinity in our model is as follow: a2>a1>b1>b2.

The interaction between propranolol (PROP) and human serum albumin (HSA) was studied in the presence of dimethyl methylphosphonate (DMMP). DMMP is usually considered as a simulant for chemical warfare agents (CWAs). For this purpose fluorescence quenching, resonance light scattering (RLS), synchronous, three-dimensional fluorescence spectroscopy and molecular dynamics (MD) simulation were employed under physiological conditions. Fluorescence spectroscopy showed that DMMP could quench, and PROP increased intensity of the HSA fluorescence spectra. The presence of DMMP remarkably decreased binding constant of PROP to HSA. Therefore, by decreasing the amount of drugs transported to its target, the free drug concentration of the target would be raised, increasing the efficacy of the drug. The results of synchronous fluorescence and three-dimensional fluorescence spectra showed that the binding of PROP and DMMP to HSA induced conformational changes of HSA. According to molecular dynamics simulation results proposed that these ligands could interact with the HSA, with affecting the secondary structure of protein and with a modification of its tertiary structure.

AaCel9A [b-1,4-endoglucanase, (E.C:3.2.1.4)], was immobilized onto glutaraldehyde activated chitosan macrosphere by covalent attachment. The properties of the immobilized AaCel9A were investigated by determining the optimum pH and optimum temperature for activity, thermal stability, and kinetic parameters. The immobilization process shifted the enzyme’s optimum temperature from 65oC for the free enzyme towards a wider temperature range from 60-80oC by the immobilized enzyme. The optimum pH of immobilized AaCel9A shifted to basic pH (pH 8) relative to free AaCel9A (pH 6.5). The immobilization on chitosan macrosphere enhanced half-life of AaCel9A enzyme. After 60 min, the immobilized and the free enzyme retained 75% and 40% their activity at 65oC, respectively. The immobilized enzyme showed higher thermal stability than the free form. Km value of immobilized AaCel9A (17.05 mg ml-1) was higher than free AaCel9A (7.75 mg ml-1). Also, CMC hydrolysis by immobilized and free AaCel9A in the presence of SDS detergent was investigated. The results showed that the immobilized enzyme maintained its activity more than the free form in different concentrations of SDS.

Developing simple, sensitive and selective sensing systems for dopamine is important due to its biological significance. In this work, a silver nanoparticles-modified carbon paste electrode (AgNPs-CPE) has been constructed and used to detect of dopamine (DA) in the simultaneous presence of ascorbic acid (AA) and uric acid (UA) at neutral pH 7.0 by cyclic voltammetry. The modified electrode showed good performance toward the oxidation and determination of DA in the presence of AA and UA. In a mixture of the three compounds, DA showed a pair of redox peaks at about 182.0 and 116.0 mV for anodic and cathodic peaks potential, respectively, while AA and UA exhibited an oxidation peak at about 320.0 mV. Under these circumstances DA more easily oxidized than AA and UA at the surface of modified electrode and precisely determined by differential pulse voltammetry. A sensitivity of 0.074 mA/mM with a wide linear range of 12.5-300.0 mM and detection limit of 0.61 mM were obtained. The modified electrode was applied successfully for DA quantification in dopamine hydrochloride injection sample in the presence of AA and UA (100 mM).

The effects of electromagnetic fields (EMFs) radiation at the frequency of 940 MHz on the structure and function of human adult and fetal hemoglobin (HbA and HbF) were studied. After extraction and purification of HbA and HbF, the oxygen absorption values for exposed and unexposed HbA and HbF to EMF were compared. The slope of oxygen absorption curve for exposed HbA was increased while that for HbF was decreased compare to those before EMF exposing. Furthermore, the oxygen absorption saturation values were changed from 3.4-5.1 and from 5.1-3.1 mg l-1, respectively for HbA and HbF after exposing to EMF. The UV-Vis, circular dichroism and fluorescence spectroscopy confirmed the quaternary structural changes of both proteins after EMF exposure. So that, the structural transition of HbA from tense to relaxed state caused an increasing in oxygen absorption; whilst in HbF, transition from relaxed to tense state was occurred and therefore oxygen absorption was decreased.

Bacteriorhodopsin (BR) is a retinal protein that is a light-driven proton pump and has an important role in photosynthesis in archaebacterium Halobacterium salinarum. The BR molecule absorbs light and photochemical changes occur in it, and different intermediates will be produced in its photochemical cycle that some of them like P and Q intermediates have a long half-life. There have been many efforts to immobilize BR for constructing data storage devices. In this study the BR suspension-contained film has been immobilized on a polycarbonate and the effects of green and red lasers on it (in different times and temperatures) have been investigated by UV spectrophotometer method, The modified surfaces were characterized by ATR-FTIR and AFM techniques. The results show that with used condition for immobilization of BR on polycarbonate, the 0 and 1 bite that relate to BR and P, Q intermediate, are formed. The red and green lasers convert BR to O and, P or Q intermediates respectively that could be used instead of 0 and 1 bites in popular compact disks.

To answer challenge of targeted and controlled drug release in oral delivery various materials were studied by different methods. In the present paper, controlled metal based drug (Pd(II) complex) release manner of b-Lactoglobulin (b-LG) nanoparticles was investigated using mathematical drug release model in order to design and production of a new oral drug delivery system for gastrointestinal (GI) tract. The b-LG nanoparticles containing Pd(II) complex were fabricated in the presence of low methoxyl pectin (LMP) at different conditions. Characterization of b-LG nanoparticles using dynamic light scattering (DLS) and atomic force microscopy (AFM) were performed. The in vitro drug release studies were carried out at 37oC during 8 h in the simulation conditions of GI fluid. The obtained results were fitted in various kinetically release models. The Korsmeyer-Peppas model was evaluated the best describe of each simulation conditions such results indicated an anomalous diffusion manner for drug release. The release data were fitted to the Kopcha model; then, using statistically evaluation revealed that b-LG nanoparticles-LMP complex contain Pd(II) complex dramatically sensitive to pH. In addition, results indicated that for drug release from b-LG nanoparticles delivery system erosion is predominate. So, the erosion-controlled is drug release mechanism of this delivery system. We concluded that b-LG nanoparticles complex with LMP based on mathematical drug release model would be a targeted and practical promising device for GI drug delivery.

Under prolonged diabetic conditions, HbA1c is produced from normal hemoglobin (HbA0) through a non-enzymatic glycosylation or glycation, a process which enhances the hemoglobin susceptibility to be auto-oxidized to methemoglobin (metHb). Here we are reporting that the non-enzymatic reaction between fructose and metHb (metHb fructation) induces significant changes in the globin structure and degrades the hemin moiety. Moreover, glycation of metHb by fructose brings about the extensive hypochromic effect and a small bathochromic effect in the Soret region. The products of hemin degradation were shown to be dialyzable species. Cathodic peaks of the cyclic voltammogram (CV) of methemoglobin during incubation with fructose resulted positive potential shift and the declined current at the peaks due to a decrease in the number of metHb molecules with the preserved hemin groups. Moreover, we found a significant increase in the hemin oxidation products such as ferryl/oxoferryl-Hb upon fructation of metHb. The production of such species during metHb fructation and hemin degradation might have a key role not only in the induction of hypoxic stress, but also in the reduced protective function of neural hemoproteins in Alzheimer’s disease (AD).

Curcumin is a natural substance with anti-cancerous properties without many disadvantages of currently-used anticancer drugs. Its toxicity is significantly higher in tumor cells compared with normal cells. We hypothesized the difference of p53 function between normal and tumor cells as one of the presumable causes of this phenomenon. We knocked down the expression of p53 in normal fibroblasts using anti-p53 siRNA and subsequently explored the effects caused by dendrosomal curcumin- a novel nanoformulation of curcumin- on these cells in terms of apoptosis induction and gene expression analysis. The results of MTT assay demonstrated dendrosomal curcumin is selectively cytotoxic for melanoma cancer cells without any considerable effects on normal fibroblasts. Knocking-down of p53 in normal fibroblast cells caused increase of NF-kB1 and decrease of p21 expression level. Treating p53-suppressed normal fibroblast cells with dendrosomal curcumin led to a robust increase in apoptosis rate of the cells. Taken together, these results imply the fact that p53 can protect normal cells from dendrosomal curcumin-induced apoptosis. Therefore, dendrosomal curcumin- in addition to being a chemotherapeutic compound-represents potential capacities to be used as an effective chemopreventive agent.

Interactions of 3,3’,4,4’-tetrahydroxybiphenyl (BPT) and three isomeric 3,3”,4,4”-tetrahydroxyterphenyls (OTT, MTT, PTT) with Alzheimer’s amyloid-b peptide (Ab) were studied by molecular dynamics simulation and molecular docking. Structural parameters such as Root-mean-square derivations (RMSD), radial distribution function (RDF), helix percentage and other physical parameters were obtained. These inhibitors have been evaluated and compared for their activity against aggregation of Ab. The results showed that all four compounds successfully inhibit association of Ab and reduce aggregation of protein. For the tetrahydroxyterphenyls efficacy varies with linker geometry: the ortho-position affords the most successful inhibition and the para-geometry the least perhaps due to differing abilities of these inhibitors to bind amyloid-b peptide. Of the four small inhibitors studied 3,3’,4,4’-tetrahydroxybiphenyl (BPT) is the most effective inhibitor. Molecular docking studies have been done to confirm the simulation results. Investigation of binding site and free energy confirmed that the efficiency of interaction with Ab depends on differing abilities of these inhibitors to bind amyloid-b peptide. Binding energy of BPT is more negative than the other and it significantly decreases for PTT. Self-aggregation of this inhibitor decreases in comparison with BPT; therefore Ab aggregation in the presence of biphenyl form is higher than terphenyls.

The ability of small molecules to perturb the natural structure and dynamics of nucleic acids is intriguing and has potential applications in cancer therapeutics. This work reports the synthesis, characterization, cytotoxicity and DNA-binding studies of two cytotoxic and intercalative [M(bpy)(pyrr-dtc)]NO3 complexes (where M=Pt(II) and Pd(II), bpy=2,2’-bipyridine and pyrr-dtc=pyrrolidinedithiocarbamate). Binding interaction of these complexes with calf thymus DNA (CT-DNA) was investigated by spectrophotometric, spectrofluorometric and gel filtration techniques. Gel filtration studies indicate that the binding of these complexes with CT-DNA is strong enough not to readily break. The binding constant and the thermodynamic parameters have been determined using absorption measurements. The fluorescence studies indicate that the two complexes bind to CT-DNA through an intercalative mode. The cytotoxic activity of these metal complexes has been tested against chronic myelocytic leukemia K562 cell lines and revealed much lower 50% cytotoxic concentration (Cc50) than that of cisplatin. We hope that such spectroscopic studies to be indeed helpful in studying the pharmacological response of drugs and design of dosage forms.