The Anomalous Colligative Properties of Proline Brigitte Schobert Department of Botany, Technical University Munich, D-8000 Miinchen The iminoacid proline is of significant biological importance in water-stress resistance of diatoms and several higher plants [1]. To gain further insight into the function of proline accumulation in plant cells, some physicochemical properties of proline in aqueous solution have been investigated. Unusually high freezing-point depressions (expressed as 'osmoles' with the Knauer osmometer) have been observed in proline solutions of increasing concentrations. Figure 1 shows the molarity-osmole plot of proline in comparison with 4-hydroxyproline and glycine. With rising concentrations proline exhibits nonideality effects, which are uncommon for low-molecularweight substances. The measured activity of glyc~ne is expected and lower than its corresponding concentration, whereas the activity of proline becomes increasingly higher than its molarity and cannot be corrected by activity coefficients. 4-Hydroxyproline shows the same tendency, but a weaker effect. Likewise, only very dilute proline solutions were in agreement with the Raoult's law when vapor-pressure depression was investigated (Hewlett Packard, vapor-pressure osmometer). Concentrations exceeding 0.04 M exhibited a nonideality effect, which is consistent with the freezing-point depressure curve. These results point out that increasingly concentrated proline solutions show deviations from ideality that are common for colloidal solutions [2]. It is assumed therefore that soluted proline forms 'polymers' by stepwise stacking and hydrophobic interaction of the pyrrolidine ring, the size of the associate depending on the proline concentration. Hydrophobic nonmicellar self-association is described for solutes of similar molecular structures [3]. In the proposed arrangement the hydrophilic carboxylic and imino groups are exposed to the ' outside' of the aggregate versus water. Such colloids alter the water structure much more by the water-binding capacity of their hydrophilic groups than by their colligative function [2, 4]. Thus, the assumed association model of proline could well explain the unexpected osmotic behavior. Further unusual properties of proline solutions are under investigation [5]. 386

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Fig. 1. Molarity-osmole plot of L-proline, 5-4-hydroxyproline, and L-glyeine, measured by freezing-point depression Received March 4, 1977 1. Hellebust, J.A. : Ann. Rev. Plant Physiol. 27, 485 (1976) 2. Ahmed, A.J., et al. : J. Biol. Chem. 250, 3344 (1975)

3. Mukerjee, P. : J. Pharm. Sci. 63, 972 (1974) 4. Luck, W.A.P.: Topics Curr. Chem. 64, 113 (1976) 5. Schobert, B., Tschesche, H. : Biophys. Chem. (in preparation)

The Scales as a Releaser of the Copulation Attempt in Lepidoptera T. Ono Laboratory of Applied Entomology and Nematology, Faculty of Agriculture, Nagoya University, Chikusa, Nagoya, 464 Japan In many lepidopterous insects, sex pheromone plays an important, though partial, role in the process of copulation, which involves complex behavioral chains [1-3]. The author reported previously that in the potato tuber moth, Phthorirnaea operculeIla, the final step of the mating process, the copulation attempt with the right object, was released by the presence of scales and that the stimulus concerned seemed to be a mechanical one that resulted from

the contact of the male moth with the object covered by the scales [4].Since in many lepidopterous insects contact with the scales occurs at the final stage of the mating process, it is reasonable to assume that the role of the scales in the recognition of the right object or in the release of the copulation attempt is not peculiar to P. operculella but universal in Lepidoptera. Subsequently, the author has examined the copulation processes of the silkworm

Namrwissenschaften 64 (1977)

9 by Springer-Verlag 1977

The anomalous colligative properties of proline.

The Anomalous Colligative Properties of Proline Brigitte Schobert Department of Botany, Technical University Munich, D-8000 Miinchen The iminoacid pro...
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