Repairs on Van de Graaff

Van de Graaff & microwave bridge

Klystron, microwave bridge, & magnet

Block Diagram of ESR Spectrometer

Gravity flow system, detector, & magnet

Glycine anion controversy Steady-state  -radiolysis (1985) showed large yields of CO 2 at high pH, which suggests large yields of  CH 2 NH 2 radicals Steady-state  -radiolysis (1985) showed large yields of CO 2 at high pH, which suggests large yields of  CH 2 NH 2 radicals H 2 N-CH 2 -CO 2  +  OH  CO 2 +  CH 2 NH 2 + OH  Steady-state electron radiolysis with ESR detection (1971) saw only the capto-dative stabilized NH 2 -  CH- CO 2  radical, among the possible C-centered radicals from glycine anions Steady-state electron radiolysis with ESR detection (1971) saw only the capto-dative stabilized NH 2 -  CH- CO 2  radical, among the possible C-centered radicals from glycine anions

Scavenging Reducing Radicals with MV 2+ 1 M Gly 0.5 mM MV 2+ pH 10.6 Suggestion for “fast” component: H 2 N-CH 2 -CO 2  +  OH  CO 2 +  CH 2 NH 2 + OH   CH 2 NH 2 + MV 2+  MV  + CH 2 =NH 2 Suggestions for “slow” reactions: See Scheme on following slide Fast component dependent on [MV 2+ ] = 600 nm Time /s G(MV + ) fast slow

 OH-oxidation of glycine anions Scheme from Bonifacic, Stefanic, Hug, Armstrong, Asmus J. Am. Chem. Soc. 1998, 120,

Stochastic Simulation of Kinetics Scheme k’s from previous slide [  OH] o = 40  M pH 10.6

 OH-oxidation of glycine anions H 2 N-  CH-CO 2   CH 2 -NH G HN  -CH 2 -CO 2 

TRESR (Boxcar) H 2 N-  C(CH 3 ) 2 25 G H 2 N-C(CH 3 ) 2 CO 2  +  OH  H 2 N-  C(CH 3 ) 2 + CO 2 + OH 

Synthesis of spectrum  NH-C(CH 3 ) 2 CO 2 - H 2 N-  C(CH 3 ) 2 (sharp lines) H 2 N-C(  CH 2 )(CH 3 ) CO 2 -

Oxidation of Amino Acids - Summary TRESR resolved controversy over the fate of the radicals following the radiolytic oxidation of glycine anions TRESR resolved controversy over the fate of the radicals following the radiolytic oxidation of glycine anions Showed presence of  CH 2 NH 2 Showed presence of  CH 2 NH 2 Showed the “ immediate ” formation of the C-centered radicals Showed the “ immediate ” formation of the C-centered radicals Directly detected aminyl radicals in -methyl alanine Directly detected aminyl radicals in -methyl alanine Advantages of TRESR for these problems Advantages of TRESR for these problems TRESR permitted the detection of short-lived radicals TRESR permitted the detection of short-lived radicals Developed methodology of measuring the yield of radicals Developed methodology of measuring the yield of radicals

TRESR - yields methodology SO 3  Saturating the transition Turning newly- created spins in the external field Microwave switch Blocking signals to the detector Conc profile

Determination of microwave magnetic field  O 2 CCH=  CCO 2  P =  10 dB P =  15 dB T 1 = 16  s T 2 = 7  s H 1 = G

Spin polarization

Notre Dame Magazine (Matt Cashore)