Proton and oxygen-17 N M R relaxation rate (T1-l and T2-l) data are presented for aqueous suspensions of dark-adapted chloroplasts. It is concluded from the dependence of the proton relaxation rates (PRR) upon Mn concentration that T1-l and T2-l are determined largely by the loosely bound Mn present in the chloroplast membranes. The frequency and temperature dependences of the PRR are characteristic of Mn(I1). The effects of oxidants (e.g., ferricyanide) and reductants (e.g., tetraphenylboron) on the PRR indicate that only about one-third to one-fourth of the loosely bound Mn is present in the dark-adapted chloroplasts as T h e involvement of manganese ions in photosynthesis was first suggested in the early studies of Pirson (1937). Much later, the site of its activity was assigned to the oxygen-evolving mechanism of photosystem I1 (Kessler et al., 1957; Spence and Possingham, 1961;Cheniae and Martin, 1966;Homann, 1968). Subsequently, Kok et al. (1 970) proposed a model for oxygen evolution in which a photochemically activated intermediate accumulates up to 4 oxidizing equiv before reacting with water to produce oxygen. Manganese can exist in several oxidation states and thus it could play a central role in the charge accumulation (Cheniae, 1970; Olson, 1970;Renger, 1970;Earley, 1973). However, until recently there has been no direct experimental evidence to show that manganese changes its oxidation state during photosynthesis (Wydrzynski et al., 1976a,b).The current view is that manganese is complexed to some protein bound to the chloroplast membrane. However, attempts to isolate a manganese protein and to reconstitute oxygen evolution have failed (Cheniae and Martin, 1966; Lagoutte and Duraton, 1975;Henriques and Park, 1976). One possible exception is the stimulation of oxygen evolution by a low-molecular-weight manganese polypeptide isolated from Phormidium luridium (Tel-Or and Avron, 1974). In any event, if one wishes to study the role of manganese in oxygen evolution, it is necessary to use an experimental approach which responds to changes in situ of the manganese.The unpaired electrons of Mn(I1) can, in favorable instances, give rise to a detectable electron paramagnetic reso- Mn(II), the remainder being in a higher oxidation state@), probably Mn(II1). The frequency dependence of the PRR for the chloroplast suspensions was fitted by a simplified form of the Solomon-Bloembergen-Morgan equations, and the following parameters were obtained:s; and B = (0.9 f 0.09) X 1019. The oxygen-17 T1 and T2 data for suspensions before and after treatment with a detergent are consistent with the location of the manganese in the interior of the thylakoids. An analysis of the relaxation rates shows that the average lifetime of a water molecule inside a thylakoid is > 1 ms.nance (EPR') spectrum. However, so far there has been only one report of EPR spectra from Mn bound to chloroplasts (Siderer et al., 1977). Another possibility is that neighboring magnetic nuclei are perturbed enough by the large magnetic mom...

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143 2 = composition in W phase, mole fraction Literature Cited Subscripts and Superscripts I, 11, I11 = phase boundary arb = arbitrary E = equilibrium in = inlet out = outletGreek Letters p = density, mol/m3The rates of growth and sdution of single crystals of sodium sulfate decahydrate and anhydrous sodium sulfate were measured under conditions of low driving force and low solution velocity past the crystal. The rates of growth and solution of sodium sulfate decahydrate were found to be controlled by the rates of heat and mass transport between the crystal surface and the bulk solution. The rate of growth of anhydrous sodium sulfate was controlled by the rate of incorporation of ions into the crystal lattice at the crystal surface. This information can be used to predict the rates of phase transitions in a system containing sodium sulfate and water, where the crystal populations, nucleation rates, and the fluid mechanics at the crystal surfaces are known.The mechanical collection efficiency of a granular bed filter is determined by the flow within the bed. I n spite of the demonstrable sensitivity of existing models to their proposed flow structures, most do not attempt accurate characterization of the flow. I n particular, interstitial flow intensification and flow separation are usually neglected.In the present paper an analytic model and collection measurements are combined to examine these effects. A potential flow model is developed in which the magnitude of the flow intensification is characterized by a single "intensification parameter". The experimental data are then employed to develop a unique correlation of this parameter with Reynolds number.

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Highly purified liquid ammonia was prepared and the proton magnetic resonance spectrum was recorded as a function of temperature from about −70° to about 35°C. The line shapes were shown to be given quantitatively by the equation derived by Pople and precise values for the nitrogen—proton coupling constant and the transition probabilities connecting the 14N spin states were measured. The Bloch equations pertinent to pure 14NH3 were extended to include the possibility of chemical exchange and a means was devised to extract precise values for the rate constants for the exchange process. Solutions of KNH2 in NH3 were prepared by the decomposition of potassium—ammonia solutions with platinum black and the kinetics of the ammonia—amide proton exchange were studied as a function of temperature and concentration. The bimolecular rate constant for the exchange was found to be 1.51×107 liter/mole·sec at 25°C, the enthalpy of activation is 4.0±0.5 kcal/mole, and the entropy of activation is −12±2 eu. This large negative entropy is interpreted in terms of a sizeable reorganization of the solvent structure in the activated complex.