China
Africa
Explore chapters and articles related to this topic
Poly(rotaxane)s as building blocks for the preparation of cyclodextrin-containing membranes
Published in Y. Yagci, M.K. Mishra, O. Nuyken, K. Ito, G. Wnek, Tailored Polymers & Applications, 2020
Laurent Duvignac, André Deratani
Considerable interest in CDs comes from their ability to accommodate hydrophobic guests in water. This binding property originates from the amphiphilic nature of CDs, hydrophilic outside – hydrophobic inside. Requirements of a geometric fitting in size and shape between the CD cavity and the molecule included (or a part of it) must be fulfilled to the inclusion take place. As non-covalent bonds are formed, the binding constant is mainly related to the strength of Van der Waals forces and hydrophobic interactions. As a consequence, molecular recognition can be achieved and CDs found numerous applications in separation science. For example, geometric and optical isomers can be readily discriminated using liquid [2] and gas chromatography [3] with supports bearing grafted CDs. Advantage can be also taken of this property to perform extractions of valuable compounds or organic pollutants from aqueous solutions. Several techniques for removal and recovery by CD-complex formation have been proposed such as selective precipitation [4], liquid-liquid extraction [5] and sorption onto CD-immobilised polymer network [6].
Glossary of scientific and technical terms in bioengineering and biological engineering
Published in Megh R. Goyal, Scientific and Technical Terms in Bioengineering and Biological Engineering, 2018
Binding is the ability of molecules to stick to each other because of the exact shape and chemical nature of parts of their surfaces. Binding can be characterized by a binding constant or association constant (Ka), or its inverse, the dissociation constant (Kd).
Approaching Cancer Therapy with Ruthenium Complexes by Their Interaction with DNA
Published in Ajay Kumar Mishra, Lallan Mishra, Ruthenium Chemistry, 2018
The emission intensity of ethidium bromide (EB) is used as a spectral probe, as it shows enhanced emission intensity when it is bound to the hydrophobic part of DNA. The binding of the complexes to DNA could result in the displacement of the bound EB and could cause a decrease in emission intensity due to quenching by the paramagnetic complexes. The DNA binding propensity of complexes is measured from the reduction of the emission intensity of EB at different complex concentrations. The fluorescence spectral method using EB as a reference was used to determine the relative DNA binding properties of the complexes to calf thymus (CT) DNA in Tris-HCl/NaCl buffer. DNA concentrations, expressed with respect to mononucleotides, were determined spectrophotometrically using the reported data for a molar absorption coefficient of 6600 M−1 cm−1 at 260 nm. Fluorescence intensities of EB at λmax 601 nm with an excitation wavelength of λmax 510 nm were measured at different complex concentrations. Reduction in emission intensity was observed with the addition of complexes. The relative binding tendency of the complexes to CT DNA was determined from a comparison of the slopes of the lines in the fluorescence intensity versus complex concentration plot. The apparent binding constant (Kapp) was calculated using the equation KEB [EB] = Kapp [complex], where the complex concentration was the value at a 50% reduction of the fluorescence intensity of EB and KEB = 1.0 × 107 M−1. Binding of Ruthenium(III) complexes of formula mer-[RuCl3(dmso)(1,10-phenanthroline)] and mer-[RuCl3(dmso) (dipyrido[3,2-a:2′,3′-c] phenazine)] (dmso = dimethyl sulfoxide) with DNA has been investigated using competitive binding with EB (Tan et al., 2008). The addition of complexes to DNA, pretreated with EB, causes appreciable reduction in emission intensity relative to that observed in the absence of the complex as shown in Fig. 8.7, and shows intercalative mode of binding.
Functionalization of powdered walnut shell with orthophosphoric acid for Congo red dye removal
Published in Particulate Science and Technology, 2019
Titilope Abiodun Ojo, Adedamola Titi Ojedokun, Olugbenga Solomon Bello
The Temkin isotherm equation assumes that the fall in the heat of adsorption of all the molecules in the layer decreases linearly with coverage due to adsorbent–adsorbate interactions and that the adsorption is characterized by a uniform distribution of the binding energies. The Temkin isotherm has been applied in the following form:where qe is the amount of adsorbate adsorbed at equilibrium (mg/g), B = RT/b = Constant related to the heat capacity (L/mg), R is the Universal gas constant (8.314 J/mol K), T is the absolute temperature (K), KT is the equilibrium binding constant (L/mg), and Ce is the equilibrium concentration of adsorbate (mg/L). KT, that is, the equilibrium binding constant, increases as temperature increases. However, judging from the values of R2 (Table 5), this model does not fit the adsorption data most.
Dual colorimetric and fluorescent determination of iron (III) using a novel squaraine dye
Published in Instrumentation Science & Technology, 2018
Chen Zhang, Mengyuan Wang, Yuzhe Zhang, Zhongyu Li, Song Xu
Furthermore, a Benesi–Hildebrand plot was used to calculate the binding constant (Ka)[19] based on the abovementioned ultraviolet–visible titration results. The magnitude of the acid dissociation constant was estimated from the slope and intercept of the fitted straight line and the value of binding constant was estimated about 1.3728 × 10−4 M−1. The Benesi–Hildebrand plot of [Initial absorbance/(Initial absorbance – absorbance)] against [Fe3+]−1 showed linearity with R = 0.99336, which further supported the 2:1 (squaraine dye + Fe3+) binding model (Figure 3).[293031]
Detection of ciprofloxacin through surface plasmon resonance nanosensor with specific recognition sites
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Esma Sari, Recep Üzek, Memed Duman, Adil Denizli
where dΔR/dt is the rate change of the response signal, ΔR and ΔRmax are experimental and theoretical maximum sensor responses measured while binding of analyte molecule (Reflectivity %/s), C is the concentration (M), ka is the association rate constant (L/mol.s), kd is the dissociation rate constant (1/s), 1/n is Freundlich heterogeneity index. Binding constant, i.e. association constant KA, which can be calculated as KA = ka/kd (L/mol) and dissociation constant, KD (mol/L), is equal to 1/KA.