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A new peptide, Tc1, containing only 23 amino acids closely packed by three disulfide bridges was isolated from the Amazonian scorpion Tityus cambridgei. It blocks reversibly the Shaker B K+-channels with a Kd of 65 nM and displaces binding of noxiustoxin to mouse brain synaptosome membranes. It is the shortest known peptide from scorpion venom that recognizes K+-channels and constitutes a new structural subfamily of toxin, classified as alphaKTx 13.1.

Este trabalho é um estudo prospectivo e descritivo dos aspectos epidemiológicos e clínicos de 72 envenenamentos por escorpiões admitidos no Hospital Municipal de Santarém, Estado do Pará, Brasil, entre fevereiro de 2000 a fevereiro de 2001. Trouxeram o animal 8,3% das vítimas, os quais foram identificados como T. cambridgei. O sexo masculino foi acometido em 83,3%. A idade das vítimas e o tempo para o socorro médico foram respectivamente de 33,6±18,3 anos e 4,6±3,2 horas em média. Os membros superiores foram acometidos em 51,5% dos casos. As manifestações locais estiveram presentes em 91,7% e as sistêmicas em 98,6% dos envenenamentos. Entre os sintomas locais encontramos: parestesia em 79,2%, dor em 52,8%, e edema em 26,4% dos casos. Nas manifestações sistêmicas predominou as queixas neurológicas em 97,2% das vítimas, sendo o sintoma de sensação de "choque elétrico" pelo corpo (88,9%) o mais freqüente. No exame neurológico os sinais mais encontrados foram: mioclonias (93,0%), dismetria (86,1%), disartria (80,6%) e ataxia de marcha (70,8%). Classificou-se como moderados 76,4% dos envenenamentos, sem nenhum caso grave. Deixaram de realizar a soroterapia 32,7% dos casos moderados, por ausência de soro específico no momento do atendimento. O escorpionismo da região de Santarém mostra um comportamento clínico regional diferente daqueles descritos no Brasil e de outros locais da Amazônia e, apresenta uma clínica predominantemente neurológica, ainda não descrita na literatura brasileira. This is a descriptive and prospective study on epidemiological and clinical aspects of 72 scorpion accidents admitted to Santarém Municipal Hospital, state of Pará, Brazil, from February 2000 to February 2001. Only 8.3% brought the animal with them, identified as T. cambridgei. The majority of victims were male (83.3%). The mean age and the time of the medical help were respectively 33.6±18.3 years and 4.6±3.2 hours. The parts of the body most affected were the superior members (51.5%). Local symptoms occurred in 91.7% cases and systemic manifestations in 98.6% of the accidents. The local symptoms included: paresthesia in 79.2% cases, pain in 52.8% and edema in 26.4%. Among the systemic manifestations neurological disorders predominated in 97.2%, and the symptom of "electric shock" occurred in 88.9% patients. The most common neurological signs were: myoclonia (93%), dysmetria (86.1%), dysarthria (80.6%), and ataxia (70.8%). The accidents were classified as moderate in 76.4% without any serious cases. The specific anti-venom serum was not administered in 32.7% of the moderate cases, due to non-availability of the anti-venom serum at the time of attendance. The victims of scorpion envenomation notified at Santarém, present a different clinical and regional behavior from previous reports in Brazil and Amazonia regions. The predominantly neurological picture has not previously been described in the Brazilian literature.

Toxins that block voltage-gated potassium (Kv) channels provide a possible template for improved homology models of the Kv pore. In assessing the interactions of Kv channels and their toxins it is important to determine the dynamic flexibility of the toxins. Multiple 10 ns duration molecular dynamics simulations combined with essential dynamics analysis have been used to explore the flexibility of four different Kv channel-blocking toxins. Three toxins (Tc1, AgTx and ChTx) share a common fold. They also share a common pattern of conformational dynamics, as revealed by essential dynamics analysis of the simulation results. This suggests that some aspects of dynamic behaviour are conserved across a single protein fold class. In each of these three toxins, the residue exhibiting minimum flexibility corresponds to a conserved lysine residue that is suggested to interact with the filter domain of the channel. Thus, comparative simulations reveal functionally important conservation of molecular dynamics as well as protein fold across a family of related toxins.