It was possible to compensate for up to 85% of the series resistance without introducing oscillations GSK-3 inhibitor into the recorded currents. Data were displayed on a digital oscilloscope (310, Nicolet Instrument) and stored on the hard disk of the computer (sampling frequency 33.3 kHz) for subsequent off-line analysis. Spontaneous action potentials were displayed on a digital oscilloscope (310, Nicolet Instruments, Madison, WI) and stored on a DAT (DTR-1024, Biologic Science Instruments). For current-clamp experiments, depolarizing current pulses were elicited at 0.5 Hz with a programmable stimulator (SMP 310, Biologic). Evoked action potentials were displayed

and stored on the hard disk of the computer using pClamp as described above. For current-clamp experiments,

the bathing solution contained (mM): NaCl, 200; KCl, 3.1; MgCl2, 4; CaCl2, 5; HEPES buffer, 10; pH was adjusted to 7.4 with NaOH. The recording electrode was filled with the following solution (mM): K-aspartate, 160; KF, 10; NaCl, 10; MgCl2, 1; ATP-Mg, 1; CaCl2, 0.5; EGTA, 10; HEPES buffer, 10; pH was adjusted to 7.4 with KOH. For voltage-clamp experiments, the superfusing solution used to record inward sodium currents contained (mM): NaCl, 80; Tetra-ethylammonium-chloride (TEA-Cl), 120; KCl, 3.1; CaCl2, 2; MgCl2, 7; CdCl2, 1; 4-aminopyridine (4-AP), 5; HEPES buffer, 10; pH was adjusted to 7.4 with TEA-OH. Patch-clamp electrodes were filled with an internal ID-8 solution containing (mM): CsCl, 90; CsF, 70; NaCl, 15; MgCl2, 1; ATP-Mg, 3; EGTA, 5; HEPES buffer, 10; pH was adjusted to 7.4 with CsOH. CX-5461 chemical structure Two different strategies were employed for the purification of μ-TRTX-An1a, i.e., two-dimensional ( Fig. 1) and one-dimensional ( Fig. 2) chromatography, both leading to the purification of μ-TRTX-An1a, as determined by MALDI-TOF analysis (data not shown). The first strategy brought the fraction of interest with eluent B concentrations between 28.8–32.8% and 31.3–32.8% through CIEX and RPC, respectively. The second strategy allowed the elution of the toxin at concentrations between

30 and 31% for the two stages of RPC. Samples of μ-TRTX-An1a purified by means of two-dimensional chromatography were used in the electrophysiological assays, while the samples purified by means of one-dimensional chromatography were used for primary structure determination. μ-TRTX-An1aalq was submitted to N-terminal sequencing by Edman degradation. This yielded the elucidation of the 37 N-terminal residues (Table 1). The remaining residues were elucidated by means of LC-MS-MS (not shown). On MS mode, μ-TRTX-An1aalq was visualized by means of its ions [M + 7H]+7, [M + 8H]+8, [M + 9H]+9 and [M + 10H]+10. The monoisotopic mass was determined as 5718.87 u. This fact suggested the presence of 6 cysteine residues, due to the difference of 348 u [i.e.