Silicomolybdate reaction data

Figure 5. Silicomolybdate reaction data for silicic acids, 16.6 mM SiOt pH 1.7 25°C, made from sodium silicates, 5 M ratios (R) indicated A, C, arid E sols aged 1 min andB, D, andFaged 10 dot 25°C.

Figure 8. Silicomolybdate reaction data for silicic acid sols made from diluted silicate solutions. Silicic acids of 16.6 mM S/Oj pH 1.7 25°C aged less than 15 min. Silicate solutions diluted from 5-1 M SiOz, aged 3 mo at 25°C. Dashed lines are for polymeric silica extracted into THF within 15 min.

Figure IL Silicomolybdate reaction data for silicic acid sols made from sodium silicate solutions of different indicated Si02 Nag0 ratios. Silicic acids 100 mM SiOt, pH 1.7, aged 1 min at 25°C, made from concentrated sodium silicate solu--...

Figure 13, Silicomolybdate reaction data for silica in ultrafiltrates and concentrates using filters of known pore diameters. Sol 16.6 mM SiOt made from concentrated sodium silicate (5 M. SiOg), pH 1.7 at 5 C, aged 5 min. Key A, starting sol B, filtrate C, concentrate using 1.5 and 2.0-nm pore diameters D, filtrate E, concentrate using 1.3-nm pore diameter F, filtrate and G, concentrate using 0.9-nm...

The above results imply that DCMU-type inhibitors (Group 1), have one site of action on or near the B-protein" complex that is located upon the external surface of the photosynthetic membrane. They specifically bind (non-specific binding is not taken into account) to this protein. On the other hand, ioxynil and i-dinoseb (Group 2) seem to affect another site of action on the O2 evolving system. This is located presumably on the inside of the thylakoid membrane. These two inhibitors do not lose their inhibitory potency towards electron transport because a part of their activity lies in an area that is not easily accessible to trypsin. The Group 2 inhibitors also inhibit silicomolybdate-mediated O2 evolution (data not shown). This reaction is essentially insensitive to DCMU (18) and DCMU-like inhibitors (, 16). 

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