ESR–ENDOR studies of x-irradiated glucose-1-phosphate dipotassium salt

Abstract

Single crystals of the dipotassium salt of gluocose-1-phosphate were grown out of water or deuterium oxide and x-irradiated at 4.2 °K. The products of irradiation were identified by means of ESR and ENDOR spectroscopy. In crystals grown out of water, three different alkoxy radicals were observed as oxidation products. In partially deuterated crystals only one of the aforementioned alkoxy radicals was produced. A hydroxyalkyl radical, RHĊOH was also produced by loss of hydrogen from the C6′ position. Electrons trapped at intermolecular sites were identified. The distances between the electron and the protons of the polar hydroxy groups forming the trap were deduced from ENDOR measurements and found to be relatively large, namely 1.732 and 1.738 Å.

Radiation Chemistry of Solid-State Carbohydrates Using EMR

“…The primary radiation-induced radicals in K2G1P after exposure at 4 K were studied by Locher and Box [88], who reported 3 different alkoxy radicals (A1-A3, A1 = O6(-H)), an IMTE and a C6(-H) hydroxyalkyl radical (IV) [88]. The assignment of the latter was explicitly confirmed by DFT calculations [11].…”

“…At certain orientations their resonances move far outside the spectral range of the (usually more prominent) C-centered radicals, whose spectral center hardly moves when the magnetic field is rotated (at least at X-band) and whose range and anisotropy are dominated by HF splitting. For alkoxy radicals 1.970<g x <2.0023; 2.005<g y <2.009 and 2.021<g z <2.11 have been reported [84][85][86][87][88]. Again, the smallest g value (closest to g e ) indicates the loneelectron orbital direction, while the largest g value is found along the C-O  bond.…”

“…A meta-analysis of the data, including new crystal structure determinations [117], and considering the Schonland ambiguity [115,118], showed that the assignment of A1 is reasonable and that A2 and A3 most probably correspond to alkoxy radicals at O4 and O2, respectively. In partially deuterated crystals, only A3 was observed together with the IMTE and C6(-H) [88]. Several other radicals were formed at LT, but not further analyzed.…”

“…The LT irradiation study demonstrated that 3 different alkoxy radicals (A1-A3), an IMTE and a C6(-H) (labeled IV) hydroxyalkyl radical are trapped [88]. As no thermal or optical bleaching studies were reported, details on the processes connecting these radicals to those stable at elevated temperatures are not available from experiment.…”

“…A number of studies on K2G1P crystals have been summarized in Section 6.5.2 (Table 6.10, [11,88,103,115,118,119]). …”