Driving Forces for Adsorption of Polyols onto Zeolites from Aqueous Solutions

2010 ◽  
Vol 114 (5) ◽  
pp. 1939-1945 ◽  
Author(s):  
Elizabeth E. Mallon ◽  
Aditya Bhan ◽  
Michael Tsapatsis
Keyword(s):  
Aqueous Solutions ◽  
Driving Forces

scholarly journals Removal of Methylene Blue from Aqueous Solutions by Using Nance (Byrsonima crassifolia) Seeds and Peels as Natural Biosorbents

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lorena Robles-Melchor ◽  
Maribel Cornejo-Mazón ◽  
Diana Maylet Hernández-Martínez ◽  
Gustavo F. Gutiérrez-López ◽  
Santiago García-Pinilla ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Aqueous Solutions ◽  
Driving Forces ◽  
Physical Adsorption ◽  
Point Of Zero Charge ◽  
Transfer Coefficients ◽  
Fractal Structures ◽  
Free Energy Of Adsorption ◽  
Freundlich Isotherms ◽  
Byrsonima Crassifolia

Contamination of effluents with chemicals is a serious problem that impacts human health. Methylene blue is a cationic dye found frequently in industrial and urban sewages. In this work, dried grinded seeds and peels of nance were used as biosorbents in aqueous solutions at pH 7 and 10 (simulating urban and textile effluents) finding that Langmuir and Freundlich isotherms adequately described the sorption. Adsorption efficiencies were larger than 98% in all cases and slightly lower at pH 7 due to the closeness with the point of zero charge (pzc) of seeds and peels of nance (5.96 and 3.42, respectively). In all cases, Langmuir adsorption was favorable (RLa < 1), and Gibbs free energy of adsorption was negative indicating spontaneity, and since these values were larger than −80 but lower than 0 kJ/mol, the MB removal process was mainly due to physical interactions, a characteristic of physical adsorption. No significant differences were found amongst bulk mass transfer coefficients for the adsorption of both sorbents, indicating that both bioadsorbents had the same hydrodynamic and driving forces as well as depicted similar MB-adsorbent affinities. Interaction of MB with adsorbents was corroborated by FTIR spectroscopy, and the sorption was evidenced by scanning electron microscopy and image analysis which indicated that both adsorbents had fractal structures.

scholarly journals Drug Delivery Systems: Study of Inclusion Complex Formation between Methylxanthines and Cyclodextrins and Their Thermodynamic and Transport Properties

Biomolecules ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 196 ◽  
Author(s):  
Cecília I. A. V. Santos ◽  
Ana C. F. Ribeiro ◽  
Miguel A. Esteso
Keyword(s):  
Aqueous Solutions ◽  
Inclusion Complexes ◽  
Molecular Mechanisms ◽  
Driving Forces ◽  
Drug Carrier ◽  
Partial Molar Volumes ◽  
Ternary Mixtures ◽  
Multicomponent Systems ◽  
Therapeutic Uses ◽  
Dispersion Technique

This paper presents an analysis of the molecular mechanisms involved in the formation of inclusion complexes together with some structural interpretation of drug–carrier molecule interactions in aqueous multicomponent systems comprising methylxanthines and cyclodextrins. The determination of apparent partial molar volumes ( φ V ) from experimental density measurements, both for binary and ternary aqueous solutions of cyclodextrins and methylxanthines, was performed at low concentration range to be consistent with their therapeutic uses in the drug-releasing field. The estimation of the equilibrium constant for inclusion complexes of 1:1 stoichiometry was done through the mathematical modelling of this apparent molar property. The examination of the volume changes offered information about the driving forces for the insertion of the xanthine into the cyclodextrin molecule. The analysis on the volumes of transfer, Δ φ V , c , and the viscosity B-coefficients of transfer, ΔB, for the xanthine from water to the different aqueous solutions of cyclodextrin allowed evaluating the possible interactions between aqueous solutes and/or solute–solvent interactions occurring in the solution. Mutual diffusion coefficients for binary, and ternary mixtures composed by xanthine, cyclodextrin, and water were measured with the Taylor dispersion technique. The behavior diffusion of these multicomponent systems and the coupled flows occurring in the solution were analyzed in order to understand the probable interactions between cyclodextrin–xanthine by estimating their association constants and leading to clearer insight of these systems structure. The measurements were performed at the standard (298.15 ± 0.01) K and physiological (310.15 ± 0.01) K temperatures.

scholarly journals INVESTIGATION OF INTERACTION BETWEEN L-HISTIDINE AND HETEROCYCLIC SUBSTANCES IN AQUEOUS SOLUTIONS BY UV SPECTROSCOPY

2018 ◽  
Vol 61 (8) ◽  
pp. 10
Author(s):  
Valentin G. Badelin ◽  
Galina N. Tarasova ◽  
Elena Yu. Tyunina ◽  
Svetlana A. Bichkova
Keyword(s):  
Aqueous Solutions ◽  
Nicotinic Acid ◽  
Drug Transport ◽  
Driving Forces ◽  
Ph Value ◽  
Uv Spectroscopy ◽  
Spectral Characteristics ◽  
Equilibrium Mixture ◽  
Stable Complex ◽  
Target Cells

Drug – macromolecular interactions are an important phenomenon in multicomponents physiological media, such as blood, membranes, intra- and extracellular fluids, etc. The investigation of the mechanisms and driving forces for the molecular processes of the complexes formation, drug transport, and their delivery to target-cells is one of the priority tasks of chemistry, biology and pharmacology. It is imperative that one first investigate the properties of model compounds of macromolecules in an aqueous medium before beginning studies of the more complex systems. The features of their behavior essentially determine the biological activity of macromolecules. One of the well recognized approaches to the study of molecular interactions in fluids is the use of spectroscopic methods. As part of the longer term objective to investigate different aspects of interaction processes between model substances of protein and drug precursor, we report the results of spectroscopic investigation of aqueous solutions containing heterocyclic compounds – L-hystidine, nicotinic acid and uracil at fixed pH value. The electronic absorption spectrums of L-histidine were obtained for aqueous solutions with nicotinic acid and uracil at pH = 7.3 and T=296 K by UV spectroscopy. The spectral characteristics of the interaction between L-histidine and nicotinic acid or uracil were determined. The binding constants and the stoichiometry of the complexes were calculated on the basis of the saturation curves. The calculation of the equilibrium mixture of ionic forms of the studied amino acid as a function of the pH of the medium was carried out according to the computer program RRSU. The forms of reagents existence in an aqueous solution with pH = 7.3 have been determined. The specific features of the interactions of histidine with nicotinic acid and uracil were founded. It was shown that the interaction of histidine with uracil leads to the somewhat more stable complex formation than one with nicotinic acid.

Collapse Transitions of Proteins and the Interplay Among Backbone, Sidechain, and Solvent Interactions

2018 ◽  
Vol 47 (1) ◽  
pp. 19-39 ◽  
Author(s):  
Alex S. Holehouse ◽  
Rohit V. Pappu
Keyword(s):  
Aqueous Solutions ◽  
Driving Forces ◽  
Three Dimensional ◽  
Polymer Physics ◽  
Solvent Interactions ◽  
Intrinsically Disordered ◽  
The Past ◽  
Collapse Transitions

Proteins can collapse into compact globules or form expanded, solvent-accessible, coil-like conformations. Additionally, they can fold into well-defined three-dimensional structures or remain partially or entirely disordered. Recent discoveries have shown that the tendency for proteins to collapse or remain expanded is not intrinsically coupled to their ability to fold. These observations suggest that proteins do not have to form compact globules in aqueous solutions. They can be intrinsically disordered, collapsed, or expanded, and even form well-folded, elongated structures. This ability to decouple collapse from folding is determined by the sequence details of proteins. In this review, we highlight insights gleaned from studies over the past decade. Using a polymer physics framework, we explain how the interplay among sidechains, backbone units, and solvent determines the driving forces for collapsed versus expanded states in aqueous solvents.

Aggregation behavior of tetrakis(N, N′, N″, N‴-tetramethyl tetra-2,3-pyridino)porphyrazine copper(II) and its interaction with ct-DNA: a thermodynamic approach

2010 ◽  
Vol 14 (04) ◽  
pp. 354-360
Author(s):  
Hamid Dezhampanah ◽  
A. Khalegh Bordbar ◽  
Zaynab Salimian ◽  
Elham Safaei
Keyword(s):  
Optical Absorption ◽  
Aqueous Solutions ◽  
Driving Forces ◽  
Hydrophobic Interactions ◽  
Binding Mode ◽  
Resonance Light Scattering ◽  
Groove Binding ◽  
Association Behavior ◽  
Hoff Equation ◽  
Thermal Melting

The association behavior of tetrakis( N , N ′, N ″, N ‴-tetramethyl tetra-2,3-pyridino)porphyrazine copper(II) ([ Cu(II) 2,3- tmtppa ]4+) was investigated in aqueous solutions at 25 °C and various ionic strengths using optical absorption and resonance light scattering (RLS) spectroscopies. The results show that ([ Cu(II) 2,3- tmtppa ]4+) does not have any affinity for aggregation due to increasing of salt concentration and exists as monomers even in homogeneous aqueous solutions of high ionic strengths (more than 1 M NaCl ). Interaction of ([ Cu(II) 2,3- tmtppa ]4+) with calf thymus DNA has also been studied in 1 mM aqueous phosphate buffer of pH 7.0, by optical absorption and RLS spectroscopies, and thermal denaturation experiments. The appearance of hypochromicity of less than 10% and bathochromicity shift of Δλ ≤ 2 nm in UV-vis spectra of ([ Cu(II) 2,3- tmtppa ]4+), increasing of thermal melting point of DNA, and no change in RLS spectra of porphyrazine due to interaction with DNA, represent the minor outside groove binding mode without any stack aggregate formation. The thermodynamic of the binding of ([ Cu(II) 2,3- tmtppa ]4+)-DNA also has been studied. The binding constant (K) was obtained by analysis of the optical absorption spectra of the complex at various DNA concentrations using SQUAD software. The value of K was estimated to be 2.34 × 105 ± 0.06 M -1 at 25 °C. The thermodynamic parameters were calculated by van't Hoff equation. The enthalpy and entropy changes were 41.83 ± 3.28 kJ/mol and 242.08 ± 9.88 J/mol.K at 25 °C, respectively. The results indicate that the process is entropy-driven and suggest that hydrophobic interactions are the main driving forces for the complex formation. Increasing of the ionic strength due to addition of NaCl destabilized porphyrazine-DNA complexes, indicating the competition of Na + ions with porphyrazine complexes for occupation of minor groove binding sites.

Ultrathin frozen sections of yeast without aldehyde prefixation

1978 ◽  
Vol 36 (2) ◽  
pp. 58-59
Author(s):  
K. J. Böhm ◽  
a. E. Unger
Keyword(s):  
Aqueous Solutions ◽  
Biological Material ◽  
Yeast Cells ◽  
Frozen Sections ◽  
Good Preservation ◽  
Ultrathin Frozen Sections

During the last years it was shown that also by means of cryo-ultra-microtomy a good preservation of substructural details of biological material was possible. However the specimen generally was prefixed in these cases with aldehydes.Preparing ultrathin frozen sections of chemically non-prefixed material commonly was linked up to considerable technical and manual expense and the results were not always satisfying. Furthermore, it seems to be impossible to carry out cytochemical investigations by means of treating sections of unfixed biological material with aqueous solutions.We therefore tried to overcome these difficulties by preparing yeast cells (S. cerevisiae) in the following manner:

Solute redistribution during in-situ irradiation of alloys in the high voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 370-371
Author(s):  
P. R. Okamoto ◽  
N.Q. Lam ◽  
R. L. Lyles
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Driving Forces ◽  
Solute Diffusion ◽  
Solute Redistribution ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Thin Foils ◽  
Solute Atoms

During irradiation of thin foils in a high voltage electron microscope (HVEM) defect gradients will be set up between the foil surfaces and interior. In alloys defect gradients provide additional driving forces for solute diffusion since any preferential binding and/or exchange between solute atoms and mobile defects will couple a net flux of solute atoms to the defect fluxes. Thus, during irradiation large nonequilibrium compositional gradients can be produced near the foil surfaces in initially homogeneous alloys. A system of coupled reaction-rate and diffusion equations describing the build up of mobile defects and solute redistribution in thin foils and in a semi-infinite medium under charged-particle irradiation has been formulated. Spatially uniform and nonuniform damage production rates have been used to model solute segregation under electron and ion irradiation conditions.An example calculation showing the time evolution of the solute concentration in a 2000 Å thick foil during electron irradiation is shown in Fig. 1.

Imaging polymers, proteins and dna in aqueous solutions with the atomic force microscope

1989 ◽  
Vol 47 ◽  
pp. 32-33
Author(s):  
S.A.C. Gould ◽  
B. Drake ◽  
C.B. Prater ◽  
A.L. Weisenhorn ◽  
S.M. Lindsay ◽  
...  
Keyword(s):  
Amino Acids ◽  
Dna Sequencing ◽  
Aqueous Solutions ◽  
Atomic Force Microscope ◽  
Piezoelectric Crystal ◽  
Atomic Force ◽  
Structure Of Molecules ◽  
Optical Lever

The atomic force microscope (AFM) is an instrument that can be used to image many samples of interest in biology and medicine. Images of polymerized amino acids, polyalanine and polyphenylalanine demonstrate the potential of the AFM for revealing the structure of molecules. Images of the protein fibrinogen which agree with TEM images demonstrate that the AFM can provide topographical data on larger molecules. Finally, images of DNA suggest the AFM may soon provide an easier and faster technique for DNA sequencing.The AFM consists of a microfabricated SiO2 triangular shaped cantilever with a diamond tip affixed at the elbow to act as a probe. The sample is mounted on a electronically driven piezoelectric crystal. It is then placed in contact with the tip and scanned. The topography of the surface causes minute deflections in the 100 μm long cantilever which are detected using an optical lever.

Chronic Pain: Fundamental Scientific Considerations, Specifically for Legal Claims

2013 ◽  
Vol 18 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Robert J. Barth
Keyword(s):  
Health Outcomes ◽  
Pain Perception ◽  
Driving Forces ◽  
Psychological Treatment ◽  
Dominant Role ◽  
Meta Analysis ◽  
General Medicine ◽  
Pain Syndrome ◽  
Problematic Relationship

Abstract Scientific findings have indicated that psychological and social factors are the driving forces behind most chronic benign pain presentations, especially in a claim context, and are relevant to at least three of the AMA Guides publications: AMA Guides to Evaluation of Disease and Injury Causation, AMA Guides to Work Ability and Return to Work, and AMA Guides to the Evaluation of Permanent Impairment. The author reviews and summarizes studies that have identified the dominant role of financial, psychological, and other non–general medicine factors in patients who report low back pain. For example, one meta-analysis found that compensation results in an increase in pain perception and a reduction in the ability to benefit from medical and psychological treatment. Other studies have found a correlation between the level of compensation and health outcomes (greater compensation is associated with worse outcomes), and legal systems that discourage compensation for pain produce better health outcomes. One study found that, among persons with carpal tunnel syndrome, claimants had worse outcomes than nonclaimants despite receiving more treatment; another examined the problematic relationship between complex regional pain syndrome (CRPS) and compensation and found that cases of CRPS are dominated by legal claims, a disparity that highlights the dominant role of compensation. Workers’ compensation claimants are almost never evaluated for personality disorders or mental illness. The article concludes with recommendations that evaluators can consider in individual cases.

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