The selectivity filter of K(+) channels is conserved throughout all kingdoms of life. Carbonyl groups of highly conserved amino acids point toward the lumen to act as surrogates for the water molecules of K(+) hydration. Ion conductivity is abrogated if some of these carbonyl groups flip out of the lumen, which happens (i) in the process of C-type inactivation or (ii) during filter collapse in ...

The migration of B16 melanoma cells into porous nitrocellulose filters fitted between the upper and lower compartments of blindwell chemotactic chambers was examined by light microscopy. Human plasma fibronectin placed in the lower compartment of such chambers enhanced in a time-, temperature-, and dose-dependent manner the directed migration of B16 cells into the filter. Fibronectin placed eit...

Attachment of tumor cells to endothelial cells is critical for migration of tumor cells out of the vascular system to establish metastases. We have studied human melanoma cell (C8161) adhesion and migration in response to stimulation by soluble collagen IV (CIV) using a modified Boyden chamber. In this modified chamber, shear flow can be introduced over the cell-substrate interface affecting tu...

Turgor-mediated leaf movements of the legume Samanea saman are associated with the migration of K(+) and Cl(-) between opposing sides of the motor organs (pulvini). We have investigated the pathway of this ion migration by localizing K(+) and Cl(-) within the secondary pulvinus at various times during leaf movements. Ion distributions in freeze-dried cryosections of pulvini were determined by s...

This paper introduces a fast high-resolution imaging algorithm designed for ultra-wideband radar, and combines modified Kirchhoff migration and frequency-wavenumber (F-K) migration. The proposed algorithm also uses the texture method and inverse boundary scattering transform to calculate efficiently the integral arising in modified Kirchhoff migration, and thus enabling the integral in the F-K ...

Consider the subband coder of figure 1, consisting of k = 0, 1, ..., M − 1 channels. Each channel has an analysis filter H k (z), a synthesis filter F k (z), down/up-sampling ratio m k , and a b k bit quantizer. The input is x[n], after passing through the analysis filters it becomes x k [n], and the subband signals are x k [n]. The subband coder is maximally decimated, M −1 k=0 m k = 1. (1) As...

The X-ray structure of KcsA, a eubacterial potassium channel, displays a selectivity filter composed of four parallel peptide strands. The backbone carbonyl oxygen atoms of these strands solvate multiple K(+) ions. KcsA structures show different distributions of ions within the selectivity filter in solutions containing different cations. To assess the interactions of cations with the selectivi...

In this paper, we introduce a new position-dependent smoothness-increasing accuracy-conserving (SIAC) filter that retains the benefits of position dependence as proposed in van Slingerland et al. (SIAM J Sci Comput 33:802–825, 2011) while ameliorating some of its shortcomings. As in the previous position-dependent filter, our new filter can be applied near domain boundaries, near a discontinuit...

We previously demonstrated that the outer vestibule of activated Kv2.1 potassium channels can be in one of two conformations, and that K(+) occupancy of a specific selectivity filter site determines which conformation the outer vestibule is in. These different outer vestibule conformations result in different sensitivities to internal and external TEA, different inactivation rates, and differen...