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We studied the mechanism by which the peptide omega-grammotoxin-SIA inhibits voltage-dependent calcium channels. Grammotoxin at concentrations of > 50 nM completely inhibited inward current carried by 2 mM barium through P-type channels in rat cerebellar Purkinje neurons when current was elicited by depolarizations up to +40 mV. However, outward current(More)
omega-Grammotoxin SIA, a peptidergic blocker of voltage-sensitive calcium channel (VSCC) responses, was purified from Grammostola spatulata (tarantula spider) venom by reverse phase high performance liquid chromatography. Protease-sensitive biological activity was monitored by determining the inhibition of K(+)-stimulated influx of 45Ca2+ into rat brain(More)
The peptide Ca2+ channel antagonists omega-conotoxin (omega-CTX) MVIIC and omega-grammotoxin (omega-GTX) SIA were studied by measuring their effects on the release of [3H]glutamate from rat brain synaptosomes. The pseudo-first-order association constant for omega-CTX MVIIC (1.1 x 10(4) M-1 sec-1) was small, relative to that for omega-GTX SIA (3.6 x 10(5)(More)
We analyze the security of the iterated Even-Mansour cipher (a.k.a. key-alternating cipher), a very simple and natural construction of a blockcipher in the random permutation model. This construction, first considered by Even and Mansour (J. Cryptology, 1997) with a single permutation, was recently generalized to use t permutations in the work of Bogdanov(More)
We show how to construct an ideal cipher with n-bit blocks and n-bit keys (i.e. a set of 2 n public n-bit permutations) from a small constant number of n-bit random public permutations. The construction that we consider is the single-key iterated Even-Mansour cipher, which encrypts a plaintext x ∈ {0, 1} n under a key k ∈ {0, 1} n by alternatively xoring(More)
The r-round (iterated) Even-Mansour cipher (also known as key-alternating cipher) defines a block cipher from r fixed public n-bit permutations P1,. .. , Pr as follows: given a sequence of n-bit round keys k0,. .. , kr, an n-bit plaintext x is encrypted by xoring round key k0, applying permutation P1, xoring round key k1, etc. The (strong) pseudorandomness(More)
We study the security of key-alternating Feistel ciphers, a class of key-alternating ciphers with a Feistel structure. Alternatively, this may be viewed as the study of Feistel ciphers where the pseudoran-dom round functions are of the form Fi(x ⊕ ki), where ki is the (secret) round key and Fi is a public random function that the adversary is allowed to(More)
Field-potential stimulation of rat dorsal-root ganglion (DRG) neurons evoked action-potential-mediated transient increases in intracellular free calcium concentration ([Ca2+]i) as measured by indo-1-based microfluorimetry. Field-potential-evoked [Ca2+]i transients were abolished by tetrodotoxin, and their dependence on stimulus intensity exhibited an abrupt(More)