Molecular weight, Calculation Determination

Kojic acid is readily soluble in water, ethanol, and acetone sparingly soluble in ether, ethyl acetate, chloroform, and pyridine and difficultly soluble in most other liquids.4-T It has been purified by recrystallization from acetone,7 ethanol-ether,20 and methanol-ethyl acetate26 also, by sublimation under diminished pressure at8-26-64 150-200°C. The m. p. (in °C.) has been given as 151-152,20-42 152,3-21-64 152.6,37 152-153,43 153-154,29 -31 and 154.6-6 The molecular weight was determined by the cryo-scopic method,4- 7-31 and the values obtained agreed well with the calculated value of 142. 

Selected entries from Methods in Enzymology [vol, page(s)] Association constant determination, 259, 444-445 buoyant mass determination, 259, 432-433, 438, 441, 443, 444 cell handling, 259, 436-437 centerpiece selection, 259, 433-434, 436 centrifuge operation, 259, 437-438 concentration distribution, 259, 431 equilibration time, estimation, 259, 438-439 molecular weight calculation, 259, 431-432, 444 nonlinear least-squares analysis of primary data, 259, 449-451 oligomerization state of proteins [determination, 259, 439-441, 443 heterogeneous association, 259, 447-448 reversibility of association, 259, 445-447] optical systems, 259, 434-435 protein denaturants, 259, 439-440 retroviral protease, analysis, 241, 123-124 sample preparation, 259, 435-436 second virial coefficient [determination, 259, 443, 448-449 nonideality contribution, 259, 448-449] sensitivity, 259, 427 stoichiometry of reaction, determination, 259, 444-445 terms and symbols, 259, 429-431 thermodynamic parameter determination, 259, 427, 443-444, 449-451. 

For characterization, the polymer is dissolved in methylene chloride, precipitated again in methanol and dried at 50 °C in vacuum.The limiting viscosity number is determined in tetrahydrofuran at 20 °C and the molecular weight calculated (see Sect. 2.3.3.3.1). Additional information can be obtained by infrared spectroscopy.There should be no absorption of the OH-group at -3400 cm . 

The ratio of calculated [ j] to experimental [77] is 1.020. This result is in strong contrast to the molecular weight values determined from the... 

Unlike polymeric j( 75-C5H5)2ZrH2 x, pale yellow ( -CsMes ZrH (7) is very soluble in hydrocarbons and ethers. Its molecular weight (cryoscopically determined for 112 mg of 7 per g of benzene as 369 calculated as 364), analytical data, NMR spectrum (Table I), and ir spectrum (y(Zr-H) 1555 cm-1 (ms. br) ... 

The most convincing evidence is Vofsi and Tobolsky s (24) work with 14C-labelled triethyloxonium tetrafluoroborate at 0°C. They found good agreement among the molecular weights calculated from the amounts of catalyst charged, determined by 14C end-group analysis and determined by vapor pressure osmometry. Dreyfuss et al. have also obtained NMR data on this initiation reaction (9). The spectra are entirely consistent with Reaction 4. No side reactions are indicated. 

The molecular weight is determined by the amino acid sequence of the protein, any post-translational modifications such as glycosylation, and the presence of bound nonpeptide groups such as metals and cofactors. While the exact weight of a polypeptide chain can be calculated from its amino acid sequence, a rule-of-thumb calculation, based on the proportion of different amino acids found in most proteins, gives the molecular weight as the number of residues multiplied by 110. 

Composition and Structure.—The molecular weight and structure have been deduced in the usual manner from physical constants. The vapour density, as determined by Hofmann s method, varied between 7-67 and 7-88 (air = l) at temperatures between 182° and 184° C., which corresponds to a molecular weight which is represented by the formula P g.1 This agrees with the molecular weight calculated from the lowering of the freezing-point of benzene. 

UV spectroscopy shows that quaternary phosphonium ions are present but, of course, does not prove that they are joined to polymer chains. The authors fractionated their polymers with a THF/water solvent-non solvent combination. They had found that the model compound described above could be quantitatively separated from phosphorus free poly(methylenemalonie ester). After fractionation the phosphorus content fell, but when the molecular weight was determined by vapour pressure osmometry, it was found that there was approximately one phosphonium group per chain. The absorption coefficient of the model compound was used to calculate the phosphorus content of the product. 

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