Photoresponse of bacteriorhodopsin immobilized in polyacrylamide gel membranes

Eroğlu, İnci; Aydemir, Adnan; Türker, Lemi; Yücel, Ayşe Meral

doi:10.1016/0376-7388(93)e0138-a

Cited by 11 publications

(4 citation statements)

References 9 publications

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“…This photocycle is initiated when the retinal is hit by a photon inducing conformational changes from all-trans to 13-cis followed by four spectral intermediates (L-M-N-O) before it returns back to its ground state. These photo-induced cyclic intermediates physically are activation, proton dissociation, proton translocation, proton association, and relaxation [17]. During these primary deformations, the proton transport in this protein is performed with small movements of groups of atoms by 1Aº or less, in less than 16ms [14,15].…”

Section: Photosensitive Layermentioning

confidence: 99%

Photo-responsive hydrogel for controlling flow on a microfluidic chip

Al-Aribe

Knopf

Bassi

2006

Photonics North 2006

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One technological challenge in microfluidic system design has been controlling the directional flow of minute amounts of fluid through various narrow channels. Stimuli-responsive polymers can be used as micro control devices such as valves because these materials significantly change their volumetric properties in response to small environmental changes in pH, temperature, solvent composition, or electric field. In this paper, a bi-layered hydrogel structure is introduced as a light activated microactuator. The first layer of the device is a light sensitive polymer network containing poly(vinyl alcohol) (PVA) and the retinal protein bacteriorhodopsin (bR). The second layer is a blend of PVA hydrogel and a pH sensitive polymer polyethylenimine (PEI). When exposed to a light source with a peak response at 568 nm, the bR molecules in the first layer undergo a multistage photocycle that cause protons to be pumped into the surrounding medium. The diffusion of these similarly charged ions through the adjoining pH responsive hydrogel generates electrostatic repulsive and attractive forces which alter the osmotic pressure within the cross-linked polymer network. Depending upon the type of electrostatic forces generated, the pH sensitive hydrogel layer will swell or, alternatively, collapse. The multi-layered structure can be fabricated and inserted into the microchannel. The expanding volume of the actuating hydrogel is used to regulate flow or control leakage. Preliminary experiments on a 625mm 3 optical actuating device are presented to identify key response characteristics and illustrate the mechanism for actuation.

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Section: Photosensitive Layermentioning

confidence: 99%

Photo-responsive hydrogel for controlling flow on a microfluidic chip

Al-Aribe

Knopf

Bassi

2006

Photonics North 2006

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“…The retinal protein is the functional molecule of the bR and gives the PM its dominant purple color. When exposed to sunlight the bR undergoes a photocycle process that transports H + ions from the cytoplasm (interior) side of the cell membrane into the outer medium through transmembrane channels [9,[12][13][14]. The PM is stable over prolonged periods of light exposure and preserves its photochemical characteristics under both dry and wet conditions.…”

Section: Methods Of Actuation-photoresponsive Proton Pumpsmentioning

confidence: 99%

Ionic Polymer Microactuator Activated by Photoresponsive Organic Proton Pumps

2015

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An ionic polymer microactuator driven by an organic photoelectric proton pump transducer is described in this paper. The light responsive transducer is fabricated by using molecular self-assembly to immobilize oriented bacteriorhodopsin purple membrane (PM) patches on a bio-functionalized porous anodic alumina (PAA) substrate. When exposed to visible light, the PM proton pumps produce a unidirectional flow of ions through the structure's nano-pores and alter the pH of the working solution in a microfluidic device. The change in pH is sufficient to generate an osmotic pressure difference across a hydroxyethyl methacrylate-acrylic acid (HEMA-AA) actuator shell and induce volume expansion or contraction. Experiments show that the transducer can generate an ionic gradient of 2.5 μM and ionic potential of 25 mV, producing a pH increase of 0.42 in the working solution. The ΔpH is sufficient to increase the volume of the HEMA-AA microactuator by 80%. The volumetric transformation of the hydrogel can be used as a valve to close a fluid transport micro-channel or apply minute force to a mechanically flexible microcantilever beam.

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“…To closer explore this pumping phenomena, Eroglu et al (1994) immobilized bR material in a 4-mm-thick polyacrylamide gel membrane using the electric field sedimentation (EFS) technique. The functionality of the modified gel membrane was tested by pumping protons between two liquid-filled compartments.…”

Section: Embedded Br Proton Pumpsmentioning

confidence: 99%

Fabrication of an optically driven pH gradient generator based on self-assembled proton pumps

Al-Aribe

Knopf

Bassi

2011

Microfluid Nanofluid

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Optically manipulating the local pH of a target solution in a microchannel, or reservoir, provides a mechanism for activating and controlling a variety of biological and chemical processes on Lab-on-a-Chip (LOC) devices and micro-total analysis systems (l-TAS). A microscale pH gradient generator that exploits the lightactivated molecular proton pumps found in the purple membranes (PM) of bacteriorhodopsin is described in this paper. The photo-electro-chemical transducer is an ultrathin layer (*13 nm) of oriented PM patches self-assembled on an Au-coated porous substrate. A biotin labeling and streptavidin molecular recognition technique is used to ensure that the extracellular side of all PM patches is attached to the porous substrate enabling unidirectional and efficient transport of ions across the transducer surface. The photo-induced proton pumps generate a flow of ions that produce a measurable change in pH between the separated solutions. The self-assembly procedure is experimentally quantified based on the capacitance characteristics of the bR membranes. The investigation confirms that the transducer is covered with the bR proton pumps at a mass density of 2.33 ng/cm 2 . Experimental tests also show that the proposed transducer can repeatedly generate pH gradients as high as 0.42 and absolute voltage differences as high as 25 mV when illuminated by an 18 mW, 568 nm light source. Furthermore, the DpH is observed to be nonlinear with respect to light intensity and exposure time. The DpH of the target solution is sufficient to cause a phenolphthalein indicator dye to change color or an ionic hydrogel micro-valve to expand.

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Photoresponse of bacteriorhodopsin immobilized in polyacrylamide gel membranes

Cited by 11 publications

References 9 publications

Photo-responsive hydrogel for controlling flow on a microfluidic chip

Photo-responsive hydrogel for controlling flow on a microfluidic chip

Ionic Polymer Microactuator Activated by Photoresponsive Organic Proton Pumps

Fabrication of an optically driven pH gradient generator based on self-assembled proton pumps

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