The aggregates formed by the interactions of the human lens ␤-crystallins have been particularly difficult to characterize because the ␤-crystallins comprise several proteins of similar structure and molecular weight and because their sequences were not known until recently. Previously, it could not be ascertained whether the species of various acidities were different proteins or modifications of the same proteins. The recent determination of the sequences permits calculation of molecular weights and unambiguous identification of the various ␤-crystallins and their modified forms by mass spectrometry. In this investigation, the components of the three sizes of ␤-crystallin aggregates, ␤ 1 (ϳ150,000), ␤ 2 (ϳ92,000), and ␤ 3 (ϳ46,000), were determined. The principal differences among the different ␤-crystallin aggregates was the presence of ␤A4 in ␤ 1 and ␤ 2 , but not ␤ 3 , and the length of the N-terminal extension of ␤B1. The size of the ␤-crystallin aggregate correlated with the length of the N-terminal extension of ␤B1, indicating that the flexible N terminus of ␤B1 is critical to the formation of higher molecular weight aggregates of ␤-crystallins. Separation of the components by ion exchange under non-denaturing conditions showed that ␤B2 occurs as homo-dimers and homo-tetramers as well as contributing to hetero-oligomers. Other ␤-crystallins were present only as hetero-oligomers.

A [1] and B [2], have been isolated from the aerial parts of Ziziphus lotus, together with the known alkaloids sanjoinenine [3], sanjoinine F [4], and frangufoline [51• Ziziphus lotus Lam. (Rhamnaceae) is a small tree that is widely distributed in the Jordan Valley. The genus Ziziphus comprises several species that are used in indigenous medicine for the treatment of various diseases (1-5). We report here the first chemical investigations of Z. lotus, yielding two new 14-membered frangulanine-type (6) cyclopeptide alkaloids from an extract of the aerial pans of Z. lotus. The new compounds, lotusanine A [1} and lotusanine B [2] were isolated along with the known alkaloids, sanjoinenine {31 (7), sanjoinine F [4] (7), and frangufoline [51 (8) (Table 1). Characterization of these compounds was achieved with the help of spectroscopic studies, especially mass spectrometry, which permitted conclusions to be drawn about the structural units (amino acids and styryl moiety) present in the compound and the manner in which they are linked (6,9). RESULTS AND DISCUSSIONCc of an alkaloidal fraction of the C6H6 extract of Z. lotus (see Experimental) gave an amorphous solid, lotusanine A [1]. The uv spectrum of 1 showed only terminal absorption. The ir spectrum exhibited bands for NH-(3260 cm '), amide carbonyls