Measurement units molecular mass limit

We have also determined the upper limit of deuterium incorporation in HCA II. For this purpose milligram quantities of H labeled protein were produced in defined media containing 98.8% D2O and [ Hs, 98%] sodium acetate as the sole carbon source using the optimized procedures outlined above. To quantitate the level of deuterium incorporation, we analyzed the molecular mass of purified HCA II by mass spectrometry. The molecular mass of fully protonated HCA II was measured to be 29102 +/- 2.4 (theoretical mass = 29098.9). At low pH the protein contains 2018 protons therefore, one would predict a theoretical mass increase of 2030.5 mass units upon complete deuteration. The molecular mass of protein produced in 98.8% D2O and ["H3, 98%] sodium acetate was measured to be 31133 +1-13, an increase of 2034 +/- 15 mass units, indicating above 96% deuterium incorporation. 

Varying the angle of incidence, a mode spectrum can be obtained and the effective refractive indexes calculated for both TE and TM polarizations. Adequate software allows real-time monitoring of any surface process, providing information on refractive index, thickness of the adsorbed molecular layer and adsorbed mass per unit surface. Measuring time is about 2 min per spectrum with an accuracy of 0.005° and a surface density detection limit around 1 pg/mm, which is enough for measuring small molecules. 

In order to establish experimental values for the mass units A/ it is sufficient to measure the limit, as the pressure tends to zero, of the ratio of the density of gas /, p, to the pressure p at any temperature. The molecular weight Mi can then be determined from the relation... 

It is all very well to calculate the atomic, molecular, and formula masses of atoms, molecules, and other compounds, but since we cannot weigh an individual particle, these masses have a limited usefulness. To make measurements of mass useful, we must express chemical quantities at the macroscopic level. The bridge between the particulate and the macroscopic levels is molar mass, the mass in grams of one mole of a substance. The units of molar mass follow from its definition grams per mole (g/mol). Mathematically, the defining equation of molar mass is... 

---