scholarly journals Kinetics of contraction initiated by flash photolysis of caged adenosine triphosphate in tonic and phasic smooth muscles.

1989 ◽  
Vol 94 (4) ◽  
pp. 769-781 ◽  
Author(s):  
K Horiuti ◽  
A V Somlyo ◽  
Y E Goldman ◽  
A P Somlyo
Keyword(s):  
Portal Vein ◽  
Adenosine Triphosphate ◽  
Time Course ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Isometric Force ◽  
Smooth Muscles ◽  
Regulatory System ◽  
Force Development ◽  
Caged Atp

Laser flash photolysis of caged adenosine triphosphate (ATP), in the presence of Ca2+, was used to examine the time course of isometric force development from rigor states in glycerinated tonic (rabbit trachealis) and phasic (guinea-pig ileum and portal vein) smooth muscles. Photolytic liberation of ATP from caged ATP initiated force development, at 20 degrees C, with half-time (t1/2) of 5.4 s in trachealis and 1.2-2.2 s in the phasic muscles. Prior to photolysis, some muscles were phosphorylated with ATP plus okadaic acid (an inhibitor of myosin light-chain phosphatase) or thiophosphorylated with ATP gamma S to fully activate the regulatory system, before turning on the contractile apparatus. In these prephosphorylated muscles, force development, after caged ATP photolysis, was more rapid than in the unphosphorylated muscles, but the t1/2 values for trachealis (0.8-1.1 s) were still longer than for ileum and portal-vein muscles (0.20-0.25 s). The results suggest that both the contractile machinery and the regulatory system are slower in the tonic than in the phasic smooth muscles. The time course of force development for each muscle type was sigmoidal, with an initial delay (td) of approximately 10% of the t1/2 value. Some possible chemical and mechanical origins of the delay are discussed.

scholarly journals Cross-bridge kinetics, cooperativity, and negatively strained cross-bridges in vertebrate smooth muscle. A laser-flash photolysis study.

1988 ◽  
Vol 91 (2) ◽  
pp. 165-192 ◽  
Author(s):  
A V Somlyo ◽  
Y E Goldman ◽  
T Fujimori ◽  
M Bond ◽  
D R Trentham ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Rate Of Force Development ◽  
Rapid Phase ◽  
Force Development ◽  
Caged Atp ◽  
Cross Bridge ◽  
Cross Bridges

The effects of laser-flash photolytic release of ATP from caged ATP [P3-1(2-nitrophenyl)ethyladenosine-5'-triphosphate] on stiffness and tension transients were studied in permeabilized guinea pig protal vein smooth muscle. During rigor, induced by removing ATP from the relaxed or contracting muscles, stiffness was greater than in relaxed muscle, and electron microscopy showed cross-bridges attached to actin filaments at an approximately 45 degree angle. In the absence of Ca2+, liberation of ATP (0.1-1 mM) into muscles in rigor caused relaxation, with kinetics indicating cooperative reattachment of some cross-bridges. Inorganic phosphate (Pi; 20 mM) accelerated relaxation. A rapid phase of force development, accompanied by a decline in stiffness and unaffected by 20 mM Pi, was observed upon liberation of ATP in muscles that were released by 0.5-1.0% just before the laser pulse. This force increment observed upon detachment suggests that the cross-bridges can bear a negative tension. The second-order rate constant for detachment of rigor cross-bridges by ATP, in the absence of Ca2+, was estimated to be 0.1-2.5 X 10(5) M-1s-1, which indicates that this reaction is too fast to limit the rate of ATP hydrolysis during physiological contractions. In the presence of Ca2+, force development occurred at a rate (0.4 s-1) similar to that of intact, electrically stimulated tissue. The rate of force development was an order of magnitude faster in muscles that had been thiophosphorylated with ATP gamma S before the photochemical liberation of ATP, which indicates that under physiological conditions, in non-thiophosphorylated muscles, light-chain phosphorylation, rather than intrinsic properties of the actomyosin cross-bridges, limits the rate of force development. The release of micromolar ATP or CTP from caged ATP or caged CTP caused force development of up to 40% of maximal active tension in the absence of Ca2+, consistent with cooperative attachment of cross-bridges. Cooperative reattachment of dephosphorylated cross-bridges may contribute to force maintenance at low energy cost and low cross-bridge cycling rates in smooth muscle.

Cooperative attachment of cross bridges predicts regulation of smooth muscle force by myosin phosphorylation

2004 ◽  
Vol 287 (3) ◽  
pp. C594-C602 ◽  
Author(s):  
Christopher M. Rembold ◽  
Robert L. Wardle ◽  
Christopher J. Wingard ◽  
Timothy W. Batts ◽  
Elaine F. Etter ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Time Course ◽  
Muscle Force ◽  
Regulatory System ◽  
Force Development ◽  
Cross Bridge ◽  
Cross Bridges ◽  
The Relationship ◽  
Cooperative Activation

Serine 19 phosphorylation of the myosin regulatory light chain (MRLC) appears to be the primary determinant of smooth muscle force development. The relationship between MRLC phosphorylation and force is nonlinear, showing that phosphorylation is not a simple switch regulating the number of cycling cross bridges. We reexamined the MRLC phosphorylation-force relationship in slow, tonic swine carotid media; fast, phasic rabbit urinary bladder detrusor; and very fast, tonic rat anococcygeus. We found a sigmoidal dependence of force on MRLC phosphorylation in all three tissues with a threshold for force development of ∼0.15 mol Pi/mol MRLC. This behavior suggests that force is regulated in a highly cooperative manner. We then determined whether a model that employs both the latch-bridge hypothesis and cooperative activation could reproduce the relationship between Ser19-MRLC phosphorylation and force without the need for a second regulatory system. We based this model on skeletal muscle in which attached cross bridges cooperatively activate thin filaments to facilitate cross-bridge attachment. We found that such a model describes both the steady-state and time-course relationship between Ser19-MRLC phosphorylation and force. The model required both cooperative activation and latch-bridge formation to predict force. The best fit of the model occurred when binding of a cross bridge cooperatively activated seven myosin binding sites on the thin filament. This result suggests cooperative mechanisms analogous to skeletal muscle that will require testing.

Effect of length history on contractile behavior of canine tracheal smooth muscle

1986 ◽  
Vol 250 (1) ◽  
pp. C146-C154 ◽  
Author(s):  
S. J. Gunst
Keyword(s):  
Smooth Muscle ◽  
Time Course ◽  
Smooth Muscles ◽  
Muscle Length ◽  
Rate Of Change ◽  
Tracheal Smooth Muscle ◽  
Force Development ◽  
Depressive Effect ◽  
Final Length

The effects of shortening on force redevelopment were studied in canine tracheal smooth muscles that were tonically contracted with electrical stimulation or acetylcholine. Muscle strips were suspended in vitro so that muscle length, force, and rate of change of force could be continuously monitored. The strips were rapidly shortened from different initial lengths to the same final length, at which the effects of shortening distance on force redevelopment were evaluated. Both the rate and magnitude of force redevelopment declined as the shortening distance was increased. Decreasing the activation of the muscle or increasing the prerelease contraction time enhanced the depressive effect of shortening. The time course of the latter corresponded to a decline in the velocity of unloaded shortening. However, force redevelopment was also substantially decreased by releases performed before the onset of force development. The shortening process per se had a depressive effect on both the rate and magnitude of force redevelopment in contracted canine tracheal smooth muscle, and this effect was reduced as the activation of the muscle was increased.

scholarly journals Unusually Fast bis-Histidyl Coordination in a Plant Hemoglobin

2021 ◽  
Vol 22 (5) ◽  
pp. 2740
Author(s):  
Stefania Abbruzzetti ◽  
Alex J. Barker ◽  
Irene Villar ◽  
Carmen Pérez-Rontomé ◽  
Stefano Bruno ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Rate Constants ◽  
Time Course ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Binding Constants ◽  
Laser Flash ◽  
High Reactivity ◽  
Nanosecond Laser ◽  
Ligand Rebinding

The recently identified nonsymbiotic hemoglobin gene MtGlb1-2 of the legume Medicago truncatula possesses unique properties as it generates four alternative splice forms encoding proteins with one or two heme domains. Here we investigate the ligand binding kinetics of MtGlb1-2.1 and MtGlb1-2.4, bearing two hemes and one heme, respectively. Unexpectedly, the overall time-course of ligand rebinding was unusually fast. Thus, we complemented nanosecond laser flash photolysis kinetics with data collected with a hybrid femtosecond–nanosecond pump–probe setup. Most photodissociated ligands are rebound geminately within a few nanoseconds, which leads to rates of the bimolecular rebinding to pentacoordinate species in the 108 M−1s−1 range. Binding of the distal histidine to the heme competes with CO rebinding with extremely high rates (kh ~ 105 s−1). Histidine dissociation from the heme occurs with comparable rates, thus resulting in moderate equilibrium binding constants (KH ~ 1). The rate constants for ligation and deligation of distal histidine to the heme are the highest reported for any plant or vertebrate globin. The combination of microscopic rates results in unusually high overall ligand binding rate constants, a fact that contributes to explaining at the mechanistic level the extremely high reactivity of these proteins toward the physiological ligands oxygen, nitric oxide and nitrite.

Effect of Aggregation on Bacteriochlorin a Triplet-state Formation: A Laser Flash Photolysis Study¶

2002 ◽  
Vol 76 (5) ◽  
pp. 480 ◽  
Author(s):  
Xavier Damoiseau ◽  
Francis Tfibel ◽  
Maryse Hoebeke ◽  
Marie-Pierre Fontaine-Aupart
Keyword(s):  
Triplet State ◽  
State Formation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

A Laser Flash Photolysis and Pulse Radiolysis Study of Primary Photochemical Processes of Flumequine¶

2000 ◽  
Vol 72 (4) ◽  
pp. 451 ◽  
Author(s):  
M. Bazin ◽  
F. Bosca ◽  
M. L. Marin ◽  
M. A. Miranda ◽  
L. K. Patterson ◽  
...  
Keyword(s):  
Pulse Radiolysis ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Photochemical Processes
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