Not freezing water in the lamellar system of chloroplasts.

In the course of small angle X-ray scattering analyses K r e u t z and W e b e r 1 observed that the particles of a soluble protein preparation derived from the lamellar system of chloroplasts by treatment with formic acid, exhibited an unusual high water content of 75 per cent. Viscosimetric investigation by M e n k e and R u p p e l 2 with a preparation obtained by a somewhat modified procedure also pointed to a high hydration of the protein particles. A solution of this protein had a limiting viscosity number [n] of 12 ml/g. With an axis ratio of 1:2.4 of the effective flattened hydrodynamic ellipsoid, also a hydration of 76 per cent was calculated. To our knowledge no investigations have been made' on the water content and the state of water in the thylakoid membrane, from which the above mentioned preparations have been obtained. K u n t z , B r a s s f i e l d , L a w , and P u r c e l l 3 observed by means of proton magnetic resonance spectroscopy, that in protein solutions a fraction of the water will not freeze even at —35 °C. The amount of the not freezing water is within the experi­ mental error the same as the amount of hydration water, determined by other methods. It thus appeared obvious to determine with this method the amount of the not freezing water in the lamellar system of chloroplasts. Stroma-freed chloroplasts of Antirrhinum majus, strain 50, were prepared according to an earlier described procedure4. The water signals were measured in the HR-mode with external side bands using a Yarian HA 100 nuclear resonance spectrometer. For temperature regulation the temperature unit V 6040 was used. The temperature of the sample was deter-