Three-dimensional structure of electron transfer components in photosystemII: "2+1" ESE of chlorophyll Z and tyrosine D

A "2+1" electron spin echo method has been applied to measure the orientati on of the distance vector R from the redox-active tyrosine residue Y-D to c hlorophyll Z Chl(Z) in a membrane-oriented Mn-depleted preparation of photo system II. The angle between R and the normal n to the photosystem II membr anes was determined to be 50.0 +/- 5 degrees with the value of the dipolar interaction parameter D-0 = 2.0 MHz, the corresponding distance of 29.4 +/- 0.5 Angstrom, determined in a nonoriented PS II sample.