Effect of Joule heating on isoelectric focusing of proteins in a microchannel

Yoo, Kisoo; Shim, Jaesool; Dutta, Prashanta

doi:10.1063/1.4904805

Cited by 11 publications

(17 citation statements)

References 33 publications

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“…3B-D. The conductivity and electric field distributions are inline with reports in the literature [21]. The conductivity (electric field) rise (drop) is the highest at the location of the albumin pI because of a much higher value of the square of the mean charge ( z 2 i ) for albumin compared to others (see Table 1).…”

Section: Discussionsupporting

confidence: 82%

“…One option is to compute them based on the nominal pH gradient and electric field. However, a recent numerical study shows that the electric field drops significantly at the location of focused proteins , and the deviation is very significant from the nominal electric field. Thus, it would be a mistake to use the nominal electric field for the determination of protein concentration.…”

Section: Theoretical Analysismentioning

confidence: 97%

“…In a carrier ampholyte based IEF, the local conductivity increases sharply at the location of a protein isoelectric point, which results in a decrease in the local electric field . To evaluate the local electric field at the location of a protein isoelectric point, we considered two separate IEF systems.…”

Section: Theoretical Analysismentioning

confidence: 99%

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Steady‐state protein focusing in carrier ampholyte based isoelectric focusing: Part I—Analytical solution

2017

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The determination of an analytical solution to find the steady-state protein concentration distribution in IEF is very challenging due to the nonlinear coupling between mass and charge conservation equations. In this study, approximate analytical solutions are obtained for steady-state protein distribution in carrier ampholyte based IEF. Similar to the work of Svensson, the final concentration profile for proteins is assumed to be Gaussian, but appropriate expressions are presented in order to obtain the effective electric field and pH gradient in the focused protein band region. Analytical results are found from iterative solutions of a system of coupled algebraic equations using only several iterations for IEF separation of three plasma proteins: albumin, cardiac troponin I, and hemoglobin. The analytical results are compared with numerically predicted results for IEF, showing excellent agreement. Analytically obtained electric field and ionic conductivity distributions show significant deviation from their nominal values, which is essential in finding the protein focusing behavior at isoelectric points. These analytical solutions can be used to determine steady-state protein concentration distribution for experiment design of IEF considering any number of proteins and ampholytes. Moreover, the model presented herein can be used to find the conductivity, electric field, and pH field.

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Section: Discussionsupporting

confidence: 82%

Section: Theoretical Analysismentioning

confidence: 97%

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Steady‐state protein focusing in carrier ampholyte based isoelectric focusing: Part I—Analytical solution

2017

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“…The last term on the right-hand side of Eq. (4) is the time-averaged heat generation due to Joule heating (present only inside the fluid) where the contributions from the flow and concentration induced ion transport have been neglected [45]. By the use of dimensional analysis, we find that the thermal Peclet number, Pe = RePr is smaller than 0.1 because the Reynolds number is Re ࣘ 0.01 and the Prandtl number is Pr Ͻ 10 under our experimental conditions [43,44].…”

Section: Temperature Fieldmentioning

confidence: 99%

“…As PDMS can be considered to be electrically insulating, electric field is confined inside the fluid and governed by the quasielectrostatic equation as follows:

\nabla \cdot (σ E + i ω D) = 0,

where σ is the electric conductivity of the fluid that is dependent on the concentration and mobility of ions dissolved therein ,

E = - \nabla φ

is the electric field with ϕ as the electric potential, i is the imaginary unit,

ω = 2 π f

is the angular frequency of the applied electric voltage with f as the normal frequency, and

D = ε E

is the electric field displacement with ε as the fluid's electric permittivity. Note that the convection current has been assumed to be negligible when compared with the conduction current, σE .…”

Section: Theorymentioning

confidence: 99%

Joule heating effects on electroosmotic entry flow

et al. 2016

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Electroosmotic flow is the transport method of choice in microfluidic devices over traditional pressure-driven flow. To date, however, studies on electroosmotic flow have been almost entirely limited to inside microchannels. This work presents the first experimental study of Joule heating effects on electroosmotic fluid entry from the inlet reservoir (i.e., the well that supplies fluids and samples) to the microchannel in a polymer-based microfluidic chip. Electrothermal fluid circulations are observed at the reservoir-microchannel junction, which grow in size and strength with the increasing alternating current to direct current voltage ratio. Moreover, a 2D depth-averaged numerical model is developed to understand the effects of Joule heating on fluid temperature and flow fields in electrokinetic microfluidic chips. This model overcomes the problems encountered in previous unrealistic 2D and costly 3D models, and is able to predict the observed electroosmotic entry flow patterns with a good agreement.

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Joule heating induced stream broadening in free‐flow zone electrophoresis

Dutta

2017

Electrophoresis

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The use of an electric field in free-flow zone electrophoresis (FFZE) automatically leads to Joule heating yielding a higher temperature at the center of the separation chamber relative to that around the channel walls. For small amounts of heat generated, this thermal effect introduces a variation in the equilibrium position of the analyte molecules due to the dependence of liquid viscosity and analyte diffusivity on temperature leading to a modification in the position of the analyte stream as well as the zone width. In this article, an analytic theory is presented to quantitate such effects of Joule heating on FFZE assays in the limit of small temperature differentials across the channel gap yielding a closed form expression for the stream position and zone variance under equilibrium conditions. A method-of-moments approach is employed to develop this analytic theory, which is further validated with numerical solutions of the governing equations. Interestingly, the noted analyses predict that Joule heating can drift the location of the analyte stream either way of its equilibrium position realized in the absence of any temperature rise in the system, and also tends to reduce zone dispersion. The extent of these modifications, however, is governed by the electric field induced temperature rise and three Péclet numbers evaluated based on the axial pressure-driven flow, transverse electroosmotic and electrophoretic solute velocities in the separation chamber. Monte Carlo simulations of the FFZE system further establish a time and a length scale over which the results from the analytic theory are valid.

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Effect of Joule heating on isoelectric focusing of proteins in a microchannel

Cited by 11 publications

References 33 publications

Steady‐state protein focusing in carrier ampholyte based isoelectric focusing: Part I—Analytical solution

Steady‐state protein focusing in carrier ampholyte based isoelectric focusing: Part I—Analytical solution

Joule heating effects on electroosmotic entry flow

Joule heating induced stream broadening in free‐flow zone electrophoresis

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