Time dependence of concentration distributions in sedimentation analysis

Jl, Bethune

doi:10.1021/bi00815a023

Cited by 9 publications

(8 citation statements)

References 21 publications

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“…Further, the avoidance of any assumptions in calculations of molecular weights suggest the employment of this method in the evaluation of other methods which do invoke assumptions in calculation or require ancillary experiments. Finally, as previously noted (Bethune, 1970), other applications of the method of data acquisition described here are apparent. Thus, the time derivative formulation of the equations for the approach to equilibrium should be readily approachable experimentally, a supposition presently under examination.…”

Section: Resultssupporting

confidence: 57%

“…In this context, the present communication reports the development of methodology which allows the unambiguous determination of the reduced refractometric molecular weights of macromolecules in any solvent system. The theoretical, and potential practical, advantages of the use of time-lapse motion picture photography as the primary means for data acquisition in ultracentrifuge experiments have been detailed (Bethune, 1970). The present communication provides experimental verification for the predicted utility of this approach.…”

mentioning

confidence: 80%

“…The plates were read on a Mann two-dimensional comparator, utilizing previously noted techniques (Bethune, 1965;Richards etal., 1968).…”

Section: Methodsmentioning

confidence: 99%

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Ultracentrifuge time-lapse photography. Determination of molecular weights

Simpson¹,

Bethune²

1970

Biochemistry

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Section: Resultssupporting

confidence: 57%

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confidence: 80%

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Ultracentrifuge time-lapse photography. Determination of molecular weights

Simpson¹,

Bethune²

1970

Biochemistry

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“…The Agar postulate selects the arbitrary value S* (CI-, 0.01 molal) = 0 [9] as a basis for deducing conventional ionic ~ransport entropies so that S* (K +, 0.01 molal) = S* (KC1, 0.01 molal) ---- The moving entropy S~ has a twofold concentration dependence, (i) that of ~ given by the ordinary mass action expression S~ = S~ --R In m~i --RT d in 7~/dT [10] and (ii) the further concentration dependence of S*i which is akin to that of the activity coefficient or of the ionic conductance. In dilute solutions, the concentration dependence of S*~ can be approximated by the Debye-Hfickel theory (4,12), and in more concentrated solutions, by equations of the Fuoss-Onsager form (12). These relationships show that, at infinite dilution, S*i tends to a finite limiting value S*o~ which can be calculated in principle from the Eastman electrostatic model (5) quantitated by taking a temperature derivative of the Born free energy of hydration expression to yield (2)…”

Section: ~=O~tgs*/vfmentioning

confidence: 99%

“…The moving entropy Si(m) at molality m is transforme.d, by addition of the mass action terms 1~ In m~ ~-RT d In ~/dT, to the quantity So, (m) = -~o~ -b S* ~(m) [12] which is a first approximation to the limiting standard value ~o = ~o _}_ S*o~. Here the measurable mean ion activity coefficient ~ of the salt is substituted for the unmeasurable single ion activity coefficient 7i in 1,1 salts (in binary salts of multiply charged ions, an extension of the Debye-Hiickel theory (2) suggests taking the single ion activity coefficient as 7~ : ~-z~/zj).…”

Section: ~=O~tgs*/vfmentioning

confidence: 99%

The Thermal Temperature Coefficient of the Calomel Electrode Potential Between 0° and 70°C

Bethune¹,

Daley²

1969

J. Electrochem. Soc.

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The initial thermal temperature coefficient of the calomel electrode reported in Part I is combined with the results of thermal diffusion studies elsewhere to yield information about: the entropy of transport S* of the aqueous electrolytes KCI, NaCI, LiCI, HCI, and CaCI2; the experimentally determinable moving (transported)entropy S of the ion constituents CI-, K +, Na +, Li +, H +, and Ca + +. A four-constant equation analogous to the Fuoss-Onsager conductance equation is developed for the concentration dependence of the entropy of transport S* and is applied to the salts KCI and NaCI. The division of the moving entropy S into its nonmeasurable ionic component terms: the ionic transport entropy S* and the stationary entropy S, is attempted via two postulates: the Agar postulate and the KCl-bridge postulate which give results mutually consistent within about 0.8 eu (35 ~VF/deg), e.g., S~ (H +) = --5.22 eu from our data under the Agar postulate, and --4.42 eu under the KCl-bridge postulate. These values are in good agreement with previously reported values of --4.48, --5.5, and --5.7 based on a number of alternative postulates. Values are also obtained for the transport heat capacity C* of the electrolytes and for the measurable moving heat capacity C of the --4 ion constituents at 30 ~ A division of C into its nonmeasurable ionic components: C* and C is also carried out on the basis of Fales and Mudge's hydrogen thermal emf data via the KCl-bridge posUllate, and yields, e.g., C*o ----30 eu (Cl-), 5 (H+); ~-o =--24 (CI-),--5 (H+); ~o = 6 (el-), 0 (H+). * Electrochemical Society Active Member. Key words: calomel electrode, electrolytes, entropy of transport, heat capacity of transport, ionic entropy, ionic heat capacity, ions, thermodynamic properties of salines, thermoelectric power, transported entropy, transported heat capacity.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.6.218.72 Downloaded on 2015-07-18 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.6.218.72 ABSTRACTThe moving (transported) ionic properties S and C are partial molal properties of the ion itself and include the effect of its electrical charge on that portion of the solvation layer which travels with the ion (Eastman first and second regions). The negatives of the ionic transport properties --S* and ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.6.218.72 Downloaded on 2015-07-18 to IP

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Enzyme kinetics and engineering

Carbonell

Kostin

1972

AIChE Journal

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. Particular attention is given to methods of attaching enzymes to solid supports, and to factors, such as pH and temperature, which affect the reaction rate. Recent theories accounting for the high selectivity and high rate of enzyme reactions, calculations taking into consideration the effects of diffusion, methods for analyzing kinetic data, and proposals for enzyme reactors are evaluated. Also reviewed are recent methods for extraction of enzymes from cells, procedures for synthesizing enzymes artificially, and techniques for isolating and purifying enzymes. Enzymes are of great interest to scientists and engineers not only because of their essential role in the metabolic pathways of biological systems, but also because of the vast opportunities they open up for innovations in chemical technology. Their ability to enhance the rate of chemical reactions by many orders of magnitude at room temperature and their amazing specificity towards substrates make them ideal industrial catalysts. Enzymes provide a way of eliminating many of the operational difficulties of high pressures and temperatures often encountered in chemical catalytic processes while at the same time avoiding costly and time consuming product purifications.One of the major obstacles to the industrial use of enzymes is the lack of fast, efficient methods of extracting enzymes from the cells of biological organisms. The enzyme purification methods currently available are suitable for the production of enzymes on a small scale for research applications. However, the isolation of large quantities of enzymes from microorganisms has not reached its full potential. Procedures for synthesizing enzymes artificially are being investigated, but these are still in a preliminary research stage.Enzyme reactions usually follow the well-known Michaelis-Menten kinetics under steady state conditions. The constants in the rate equation are very dependent on the physical conditions of the media in which conversion is taking place. Most enzymes exhibit an optimum pH and temperature for reaction to occur and are very sensitive to small deviations from these optimum values. The ionic strength and the presence of metal ions and inhibitors in solution can affect the rate of reaction significantly. Unusual conditions of temperature, pressure, and the presence of some organic compounds can denature the protein and completely inactivate it. The enzyme environment must therefore be carefully controlled in order to obtain the largest possible rate of conversion.In the few cases where enzymes are used industrially, the reaction is usually carried out in a homogeneous liquid phase. To isolate the products, the enzyme must be denatured by heating or by hydrolysis. It is very important to develop ways of insolubilizing enzymes to allow complete recovery of the catalyst. This would also facilitate the development of continuous heterogeneous enzymatic reaction processes. Many insolubilization procedures are being investigated, ranging from the covalent attachment of the protein to ...

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Time dependence of concentration distributions in sedimentation analysis

Cited by 9 publications

References 21 publications

Ultracentrifuge time-lapse photography. Determination of molecular weights

Ultracentrifuge time-lapse photography. Determination of molecular weights

The Thermal Temperature Coefficient of the Calomel Electrode Potential Between 0° and 70°C

Enzyme kinetics and engineering

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