Emained after our ionic blocking conditions are time independent and thus were ONO-4059 supplier excluded for the most part from integrations of the exponentially decaying currents. The integration time window, starting at voltage offset, was varied from 3 to 20 ms. Previously, we and others used a similar approach that we developed to extract NLC during stair-step protocols by integrating total capacitive current at each step and fitting the resulting Cm-Vm data to a GW610742 site two-state Boltzmann deriva-The constant of integration (off) depends on the return holding voltage and accounts for a vertical offset in the Qtot-Vm function. For fitting, we fixed linear capacitance to the average value obtained from AC admittance measures for each chloride group, since these measures provided robust, constant estimates across all frequencies (see Fig. 3). Additionally, we only report measures of integrated charge after 3 ms (10 times our clamp time constant), since earlier charge distribution at the voltage-pulse offset would be influenced by our clamp time constants of <300 ms ( Rs ?Cm). With this approach we essentially removed linear capacitive charge contamination from the total integrated charge. Fig. 1 E illustrates the equivalence of AC and time-domain estimates of Qmax. Higher resolution of prestin's frequency-dependent behavior was obtained by stimulating OHCs with voltage chirps (linear increasing frequency), with a frequency resolution of 24.41 Hz, and analyzing dualfrequency admittance, obtained by fast Fourier transform, at each component dual frequency (f1 and 2 ?f1). The stimulus consisted of voltage steps (?60 to 160 mV by 40 mV increments) superimposed with voltage chirps of 10 mV peak (4096 points at a 10 ms sampling rate, giving an Fmax of 50 kHz). One benefit of the chirp signal is that it is a multifrequency stimulus whose individual frequency components are equal in amplitude, this being accomplished by varying the phase of each frequency. Another benefit is that duration of the chirp can be easily changed (although the duration used here was only 40.96 ms). Admittance at one frequency and its harmonic were analyzed in exactly the same way as the dual-sine approach, above (see the Supporting Material Appendix). We do that at all frequencies within the chirp at a primary frequency increment of 24.41 Hz. With thisBiophysical Journal 110, 2551?561, June 7, 2016Santos-Sacchi and Song protocol, filtered responses (10 kHz four-pole Bessel) were averaged three times for each cell to reduce noise. The first chirp response during a step was discarded, since it contains a transient response. We were able to balance out stray capacitance up to a frequency of 5 kHz. This approach enabled us to construct 3D images of NLC across frequency using averages of all individual cell responses, thereby confirming and expanding on the resolution of the multi-dual-sine approach detailed above.eM measuresOHC eM data derive from our recent study on the phase relationships of eM and membrane voltage (28). Here, we present the magnitude data transformed into mechanical gain (nm/mV) so that they can be compared to sensor charge movements, i.e., NLC. Briefly, cells were whole-cell voltage clamped and eM was elicited with voltage bursts of frequency ranging from 0.024 to 6 kHz. A photodiode technique was used to measure movements of the apex of the cell, with the cell bound at its basal pole by the patch electrode. Full details can be found in (28).Kinetic modelA full description.Emained after our ionic blocking conditions are time independent and thus were excluded for the most part from integrations of the exponentially decaying currents. The integration time window, starting at voltage offset, was varied from 3 to 20 ms. Previously, we and others used a similar approach that we developed to extract NLC during stair-step protocols by integrating total capacitive current at each step and fitting the resulting Cm-Vm data to a two-state Boltzmann deriva-The constant of integration (off) depends on the return holding voltage and accounts for a vertical offset in the Qtot-Vm function. For fitting, we fixed linear capacitance to the average value obtained from AC admittance measures for each chloride group, since these measures provided robust, constant estimates across all frequencies (see Fig. 3). Additionally, we only report measures of integrated charge after 3 ms (10 times our clamp time constant), since earlier charge distribution at the voltage-pulse offset would be influenced by our clamp time constants of <300 ms ( Rs ?Cm). With this approach we essentially removed linear capacitive charge contamination from the total integrated charge. Fig. 1 E illustrates the equivalence of AC and time-domain estimates of Qmax. Higher resolution of prestin's frequency-dependent behavior was obtained by stimulating OHCs with voltage chirps (linear increasing frequency), with a frequency resolution of 24.41 Hz, and analyzing dualfrequency admittance, obtained by fast Fourier transform, at each component dual frequency (f1 and 2 ?f1). The stimulus consisted of voltage steps (?60 to 160 mV by 40 mV increments) superimposed with voltage chirps of 10 mV peak (4096 points at a 10 ms sampling rate, giving an Fmax of 50 kHz). One benefit of the chirp signal is that it is a multifrequency stimulus whose individual frequency components are equal in amplitude, this being accomplished by varying the phase of each frequency. Another benefit is that duration of the chirp can be easily changed (although the duration used here was only 40.96 ms). Admittance at one frequency and its harmonic were analyzed in exactly the same way as the dual-sine approach, above (see the Supporting Material Appendix). We do that at all frequencies within the chirp at a primary frequency increment of 24.41 Hz. With thisBiophysical Journal 110, 2551?561, June 7, 2016Santos-Sacchi and Song protocol, filtered responses (10 kHz four-pole Bessel) were averaged three times for each cell to reduce noise. The first chirp response during a step was discarded, since it contains a transient response. We were able to balance out stray capacitance up to a frequency of 5 kHz. This approach enabled us to construct 3D images of NLC across frequency using averages of all individual cell responses, thereby confirming and expanding on the resolution of the multi-dual-sine approach detailed above.eM measuresOHC eM data derive from our recent study on the phase relationships of eM and membrane voltage (28). Here, we present the magnitude data transformed into mechanical gain (nm/mV) so that they can be compared to sensor charge movements, i.e., NLC. Briefly, cells were whole-cell voltage clamped and eM was elicited with voltage bursts of frequency ranging from 0.024 to 6 kHz. A photodiode technique was used to measure movements of the apex of the cell, with the cell bound at its basal pole by the patch electrode. Full details can be found in (28).Kinetic modelA full description.
