Svedberg equation

If the rotor turns with an angular velocity co (radians per second), n molecules suspended in a liquid will experience a centrifugal force which is balanced by a frictional force Ff. The centrifugal force is expressed by 

This is the Svedberg equation. It is also the definition of the sedimentation coefficeint S. 

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It is possible to get molecular weight from the sedimentation coefficient if we assiune a conformation or if we combine with other measurements, namely the translational diffusion coefficient via the Svedberg equation [50]... 

At low rotor revolution numbers an equilibrium state can be reached between sedimentation and diffusion. Now, a time-independent concentration gradient is established, i.e., (dddt) = 0. Under these conditions, the Svedberg equation becomes ... 

The molecular weight Mr of a macromolecule can be calculated from the sedimentation coefficient using the Svedberg equation,... 

Finally the molecular weight can be determined from the well-known Svedberg equation (I)... 

Since molecular weight, MW, is equal to mQN, Equation 7.10 is converted to Equation 7.11, the Svedberg equation. 

An alternative method sometimes used to determine molecular weights of macromolecules is sedimentation equilibrium. In the previous example, using the Svedberg equation, the sample is rotated at a rate sufficient to sediment the particles. Here, the sample is rotated at a lower rate, and the particles sediment until they reach an equilibrium position at the point where the centrifugal force is equal to the frictional component opposing their movement (see Equation 7.6). The molecular weight is then calculated using Equation 7.12. 

With use of the. s 2°0w and D°o,w values cited below (Section II,D,1) an additional estimate of the molecular weight can be made by means of the Svedberg equation (18) the value obtained is 118,000. [Calculations employ as partial specific volume v = 0.745 cm3/g, obtained from the amino acid composition of the protein given in Table III (IP).]... 

Additional size estimates of the 5 M guanidine hydrochloride subunit can be made from the Svedberg equation (18), using the s°0 w and D 0.w values cited in Section II,F, and from the empirical equations of Tan-ford and associates (32, 33), which relate s and [17] values in concentrated guanidine hydrochloride solvents to polypeptide chain length. These calculations yield molecular weights of 21,300, 20,700, and 19,800, respectively, for the E. coli pyrophosphatase subunit (13). 

The Svedberg equation relates 5 to the molar mass of the particles, M2, their translational diffusion coefficient, D (related to the frictional force exerted on the particle), and to (dp/dc2)kl ... 

A rearranged Eq. (4.83) takes the form of the Svedberg equation for determining Mw by sedimentation velocity ... 

The molar mass (M) of a solute can be determined from measurements of the sedimentation coefficient, s, and the diffusion coefficient, D (see Prob. 4.18), according to the Svedberg equation ... 

The Svedberg equation was used to calculate the molecular weight from the sedimentation and diffusion coefficients ... 

We first applied the Svedberg equation to calculation of the solution molecular weight from the Sjo, as measured by velocity sedimentation, and the as measured by dynamic light... 

The molecular weight of a protein or other macromolecule can be obtained from ultracentrifugation studies. The principles involved are rather simple a high-molecular-weight molecule sediments faster and diffuses slower than a lower-molecular-weight molecule of the same density. This is expressed in the Svedberg equation ... 

The derivation of the Svedberg equation is based on the fact that a molecule in a centrifugal field will sediment at a rate so that the centrifugal force, exactly equals the sum of the buoyant force, Ft, plus the frictional force (drag), F,. 

Equation (5.5.27) is known as the Svedberg equation. If the partial specific volume of the molecules have been measured, the Svedberg equation provides a means of determining the molar mass by using the results for s and D derived... 

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