Acidity hybridization effects

The alkane propane has pATa 50, yet the presence of the double bond in propene means the methyl protons in this alkene have pATa 43 this value is similar to that of ethylene (pATa 44), where increased acidity was rationalized through sp hybridization effects. 1,3-Pentadiene is yet more acidic, having pATa 33 for the methyl protons. In each case, increased acidity in the unsaturated compounds may be ascribed to delocalization of charge in the conjugate base. Note that we use the term allyl for the propenyl group. 

Solution-based nucleic acid hybridization assays represent a class of analytical methodologies that provide for detection of target-probe hybridization events. Solution-based assays offer several advantages in comparison to configurations that use surface-bound probes, primarily from the standpoint of negating the requirement for immobilization of a probe sequence to a solid surface. Therefore, thermodynamic, kinetic and adsorptive effects that are relevant in terms of consideration of hybridization at interfaces are not encountered. Solution-based hybridization assays provide a simple way of detecting hybridization events in real-time. 

Hybridization effects The acidity of H-A increases as the percent s-character of A increases. 

Butadiyne is a stronger acid than acetylene as might be anticipated on the basis of enhanced electronegativity of j/>-hybridized carbon . As can be seen from Table 1, the dissociation of carboxylic acids is greatly enhanced by a triple bond in the a, p position, and is increased further by a second conjugated triple bond, but to a smaller extent. A third triple bond has a still smaller acid-strengthening effect- . 

The merger of traditional immunocytochemical methods with traditional nucleic acid hybridization techniques has resulted in the development of experimental approaches that serve very effectively for the detection and localization of nucleic acids in biological materials. Furthermore, these in situ methods also may serve for the molecular characterization (e.g., base composition) and quantitation (e.g., copy number) of such nucleic acids. Because of the ubiquitous occurrence of nucleic acids and the sensitivity of the detection methods, the applications are broad and diverse, and often yield information not accessible by other methods. 

Some polymers can be used as accelerators of nucleic acid hybridization. They sometimes produce background staining and are only recommended when the hybridization rate is low (small amounts of probe or target). Dextran sulfate is often used as an accelerator but polyethylene glycol (PEG 6000) and sodium polyacrylate have been shown to be valuable alternatives. These polymers probably act by exclusion of probe molecules from the volume occupied by the hydrated polymer which results in an effective increase in the probe concentration (Wetmur, 1975). The optimal probe concentration in membrane hybridization is considered to be about 10 cpm of probe/ml (1-10 ng/ml), but Amasino (1986) found a 2- to 10-fold reduction in the probe concentration to be optimal when 10% PEG was included (note that these effects may depend on the specific activity of the probe). These polymers do not act in a similar way and have their own characteristics. 

Lee, S.K., Hong, H.K., Kim, S.J., Kim, Y.K., Lee, D., Khang, G. Effects of laminated cylindrical scaffolds of keratin/poly(lactic-co-glycolic acid) hybrid film on annulus fibrous tissue regeneration. Polymer (Korea) 34,474-479 (2010)... 

The benefits of modifying EIS structures with LbL films to achieve biosensors with improved performance was also reported by Abouzar et al., who observed an amplification of the signal response upon alternating layers of polyelectrolytes and enzymes as gate membranes on the p-Si-Si02 EIS structure [99]. A new variant of EIS sensors has been produced, which comprised an array of individually addressable nanoplate field-effect capacitive biochemical sensors with an SOI (silicon-on-insulator) stmcture to determine pH and detect penicillin. It also allows for the label-free electrical monitoring of formation of polyelectrolyte multilayers and DNA (deoxyribonucleic acid)-hybridization event [100]. 

Hybridization effects are evident in the acidities of protonated amines also. The pfCa of a protonated nitrile is around -12 (an sp nitrogen), while that of pyridinium is 5.23 (sp nitrogen), and alkyl ammoniums are around 10 to 11 (sp nitrogen). 

Poologasundarampillai, G., Yu, B., Tsigkou, O., Valliant, E.M., Yue, S., Lee, P.D. et al. (2012) Bioactive silica-poly (y-glutamic acid) hybrids for bone regeneration effect of covalent coupling on dissolution and mechanical properties and febrication of porous scaffolds. Soft Matter, 8, 4822-4832. 

Eigure 3 represents an illustrative biological application an Asp Asn mutation, carried out either in solution or in complex with a protein [25,26]. The calculation uses a hybrid amino acid with both an Asp and an Asn side chain. Eor convenience, we divide the system into subsystems or blocks [27] Block 1 contains the ligand backbone as well as the solvent and protein (if present) block 2 is the Asp moiety of the hybrid ligand side chain block 3 is the Asn moiety. We effect the mutation by making the Asn side chain gradually appear and the Asp side chain simultaneously disappear. We choose initially the hybrid potential energy function to have the form... 

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