An expressed, monomeric murine myosin V construct composed of the motor domain and two calmodulin-binding IQ motifs (MD(2IQ)) was used to assess the regulatory and kinetic properties of this unconventional myosin. In EGTA, the actin-activated ATPase activity of MD(2IQ) was 7.4 +/- 1.6 s(-1) with a K(app) of approximately 1 microM (37 degrees C), and the velocity of actin movement was approximat...

Nanopore sensing has enabled label-free single-molecule measurements on a wide variety of analytes, including DNA, RNA, and protein complexes. Much progress has been made toward biotechnological applications; however, electrically probing the ion current introduces nonideal noise components. Here we further develop a method to couple an ionic current to a photon-by-photon counting of fluorescen...

The membrane excitability and contraction were examined in single barnacle muscle fibers with different internal Ca(++) concentrations by using buffer solutions made up with EGTA and Ca-gluconate in various proportions. During the passage of dc currents the membrane shows all-or-none spike potentials for internal Ca(++) concentrations below about 8 x 10(-8)M, oscillatory potential changes in th...

The rate-limiting step of cardiac muscle relaxation has been proposed to reside in the myofilament. Both the rates of cross-bridge detachment and Ca(2+) dissociation from troponin C (TnC) have been hypothesized to rate-limit myofilament inactivation. In this study we used a fluorescent TnC to measure both the rate of Ca(2+) dissociation from TnC and the rate of cross-bridge detachment from seve...

The mechanisms of recovery from inactivation of the L-type calcium current (I(Ca)) are not well established, and recovery is affected by many experimental conditions. Little is known about developmental changes of recovery from inactivation of I(Ca). We studied developmental changes of recovery from inactivation in I(Ca) using isolated adult and newborn (1-4 days) rabbit ventricular myocytes. W...

The voltage-dependent conductances of Limulus ventral photoreceptors have been investigated using a voltage-clamp technique. Depolarization in the dark induces inward and outward currents. The inward current is reduced by removing Na+ or Ca2+ and is abolished by removing both ions. These results suggest that both Na+ and Ca2+ carry voltage-dependent inward current. Inward current is insensitive...

α-Amylases are widespread enzymes that catalyze endohydrolysis of long α-1,4-glucan chains such as starch and glycogen. The highest amylolytic activity was found in 5th instar nymphs and midgut of the predatory bug, Andrallus spinidens F. (Hemiptera: Pentatomidae). The α-amylase was purified following a three-step procedure. The purified α-amylase had a specific activity of 13.46 U/mg protein, ...

We introduce a mechanism for ion sensing by MRI in which analytes compete with paramagnetic ions for binding to polydentate chelating agents. Displacement of the paramagnetic ions results in alteration of solvent interaction parameters and consequent changes in relaxivity and MRI contrast. The MRI changes can be tuned by the choice of chelator. As an example, we show that calcium-dependent disp...

Sarcolemmal perforations can be produced in bundles of rat right ventricular cells by either perfusion of the heart or soaking of the bundles with a solution containing 10 mM EGTA. All cells are affected and lose approximately 40% of the surface membrane. In these cells it is possible to show cAMP regulation of contractility (maximum Ca-activated force) without cAMP regulation of Ca sensitivity...

We describe a new technique for the separation and isolation of nonpigmented ciliary body epithelial cells from rabbit. Excised ciliary body is incubated in a medium buffered with EGTA to a free-Ca2+ concentration of 10(-8) M, and the nonpigmented cell layer is separated from the pigmented layer by microdissection under direct visualization. This technique yields intact cells which are greater ...