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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)
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)
The effects of synthetic omega-grammotoxin SIA (omega-GsTxSIA) and synthetic omega-Aga-IVA were tested in in vitro and in vivo neurochemical assays that are reflective of voltage-sensitive calcium channel function. Synthetic omega-GsTx SIA inhibited K(+)-evoked rat and chick synaptosomal 45Ca2+ flux, K(+)-evoked release of [3H]D-aspartate and(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)
Omega-Grammotoxin SIA is a peptide isolated from tarantula venom on the basis of its ability to block the voltage-gated Ca2+ channels that mediate glutamate release. To determine the Ca2+ channel subtype selectivity of omega-grammotoxin SIA, whole-cell Ba2+ current (IBa) was measured in cultured rat hippocampal neurons. Selective Ca2+ channel blockers were(More)
Exposure of synaptic plasma membranes to 50 mM ethanol in vitro brought about a 3.5 degrees C decrease in the transition temperature of the high affinity glutamate binding process in these membranes. Ethanol had no effect on the energy of activation of glutamate binding below the transition temperature but decreased the energy of activation above the(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)