Functional copolymers of N-isopropylacrylamide for bioengineering applications

As the chemistry of saccharides and related molecular species plays a significant role in the metabolic pathways of living organisms, detecting the presence and concentration of biologically important sugars in aqueous solution is necessary in a variety of medicinal and industrial contexts. The recognition of d-glucose is of particular interest, for example in the monitoring of diabetics. Recent research provides clear evidence that tight control of blood sugar levels in diabetics sharply reduces the risk of long term complications, which include blindness, kidney failure, heart attacks and even gangrene and amputation of the limbs. Current enzymatic detection methods of sugars offer specificity for only a few saccharides; additionally, enzyme based sensors are unstable in harsh conditions. Phenylboronic acid has been known for 120 years. However, it took until 1959 for the first quantitative evaluation of saccharide boronic acid interactions. Boronic acids react with 1,2 or 1,3 diols of saccharides to form five- or six-membered cyclic esters in non-aqueous or basic aqueous media. The stable boronic acid-based saccharide receptors offer the possibility of creating saccharide sensors ‘chemosensors’ which are selective and sensitive for any chosen saccharide.

Artificial Receptors as Chemosensors for Carbohydrates

http://www.jsps.org/alumni/documents/JohnFossey20101130.pdf

Boronic acid building blocks: tools for sensing and separation

L'etude demontre que les radicaux cationiques CH 3 OH +• , CH 3 NH 2 +• et CH 3 Cl +• ont des isomeres stables: • CH 2 OH 2 + , • CH 2 NH 3 + et • CH 2 ClH +

Distonic radical cations in gaseous and condensed phase

Glucose Sensing in Supramolecular Chemistry

The redox properties of ferrocene boronic acid in aqueous buffers from pH 4 to pH 12 have been investigated using cyclic voltammetry. It is shown that the proton transfer equilibrium is under thermodynamic control over the range of scan rates employed (20-5000 mV/s), leading to pKa values of 10.8 and 5.8 for the ferrocene and ferrocenium forms, respectively. In the presence of sorbitol, fructose, or glucose, the voltammetric behaviour of ferrocene boronic acid at pH 7 is consistent with reversible formation of a carbohydrate - boronic acid complex. However, in all cases, the complexation-dissociation is under kinetic control. Analysis of the voltammetric response as a function of scan rate and carbohydrate concentration, together with an independent spectroscopic determination of the binding constant to the ferrocene form, allows all of the kinetic and thermodynamic constants for each system to be determined. In general, it is found that the binding constants ferrocenium form are about two orders of magnitude greater than those for the ferrocene form. It is possible that this redox dependent switching of the carbohydrate binding can be exploited in amperometric or potentiometric sensing devices.

Redox switching of carbohydrate binding to ferrocene boronic acid

Several 4-substituted benzyl radicals of the general form R(On)SC6H4CH2•(n = 0, 1, 2; R = Me, Ph, Tol, COCH3 OCH3) have been investigated by electron spin resonance (esr) spectroscopy. In general, ...

Substituent effects on benzyl radical hyperfine coupling constants. Part 2. The effect of sulphur substituents

The effects of substituents in the meta and para positions of the benzyl radical on the α-hydrogen hyperfine coupling constants (hfc's) are discussed. The electron spin resonance (esr) spectra of t...

Substituent effects on benzylic radical hydrogen hyperfine coupling constants. Part 4. The effect of branching of the alkyl substituent

The surfaces for cis–trans isomerization and racemization of the cyclopropane radical cation (1+) are determined using abinitio calculations. It is found that polarization functions and electron co...

1,n-Radical ions: an abinitio study of racemization and isomerization of the cyclopropane radical cation

The nature of the one-electron two-centre bond in the cyclopropane and 1,2-divinylcyclopropane radical cations is elucidated by use of abinitio self consistent field (SCF) molecular orbital (MO) calculations. The charge and spin distributions in the 90,90 and 90,0 conformations are compared at the STO-3G and 4-31G basis set levels. From energy differences between the radical cations in the 90,90 conformation and the 90,0 (transition state) conformation, the activation barriers for cis–trans isomerization in the 2A1 state of C3H6,+ and of the 1,2-divinylcyclopropane radical cation are estimated. These results are compared to previous calculations and experimental data where possible.

Danial D. M. Wayner

Papers

Redox switching of carbohydrate binding to ferrocene boronic acid

Substituent effects on benzyl radical hyperfine coupling constants. Part 2. The effect of sulphur substituents

Substituent effects on benzylic radical hydrogen hyperfine coupling constants. Part 4. The effect of branching of the alkyl substituent

1,n-Radical ions: an abinitio study of racemization and isomerization of the cyclopropane radical cation

1,N-Radical ions: the nature of the one-electron, two-center bond in cyclopropane radical cations. An ab initio SCF MO approach.