Binding of an arm repeat protein to the kinase domain of the S-locus receptor kinase

Screening of a yeast two-hybrid library for proteins that interact with the kinase domain of an S-locus receptor kinase (SRK) resulted in the isolation of a plant protein called ARC1 (Arm Repeat Containing). This interaction was mediated by the C-terminal region of ARC1 in which five arm repeat units were identified. Using the yeast two-hybrid system and in vitro binding assays, ARC1 was found to interact specifically with the kinase domains from SRK-910 and SRK-A14 but failed to interact with kinase domains from two different Arabidopsis receptor-like kinases. In addition, treatment with a protein phosphatase or the use of a kinase-inactive mutant reduced or abolished the binding of ARC1 to the SRK-910 kinase domain, indicating that the interaction was phosphorylation dependent. Lastly, RNA blot analysis revealed that the expression of ARC1 is restricted to the stigma, the site of the self-incompatibility response.     

DES-GENERATED CHECKSUMS FOR ELECTRONIC SIGNATURES

Secrecy and authentication are two important features of a secure communication system. Public Key Cryptosystems, based, e.g., on the Rivest-Shamir-Adleman (RSA) algorithm, provide a very elegant solution to the problem of authenticity verification or true electronic signatures. Practical problems, however, mainly the lack of execution speed, prevent a straightforward application. In order to sign a long message it is much faster to first calculate a short digest or checksum and then sign the compressed message. For this checksum calculation the fast, inexpensive and extensively tested Data Encryption Standard (DES) can be used. But care must be taken that this additional processing step does not introduce any weakness into the signature scheme. This paper investigates two DES-based hashing methods. It is shown that neither method seems to introduce any statistical regularities in the generated checksums. The “Cipher/Message to Plain Feedback,” however, is not secure under a modification compensation attack. It is further shown how the second method, the “Cipher to Plain Feedback” proposed by Davies and Price, can be broken by a “meet in the middle attack.” This checksum method, however, can be used safely with a slight modification.     

Patterns of growth and perception: the site, the city and the wild

The natural or biological world often provides models of the simplicity, elegance and complex interactivity that we seek to impart to our technologies, buildings and artworks. Within discussions of form, materials or functionality, we look to the world of insects, animals, plants and even our own bodies for solutions and innovation. Though we may work with the organisms themselves, the first step usually involves a rupture of context, a mutation of interdependent being into a discrete object, a model for the extraction of desired characteristics. The reality of embedded wild growth, with its complexity and interrelation, has often been described in terms of infestation or of ‘nature taking over,’ a challenge to our dominance of the world. However, a closer study of this interpenetration of uncontrolled nature within spaces around us reveals our immediate surroundings to be both wilder and more alive than we often presume them to be.