Fig. 4.

Effect of disaccharide content on density of human growth hormone (hGH) formulations: comparison of experimental data for sucrose and trehalose systems with calculated effect of changing atomic density with added disaccharide. The effect of variable average atomic density was estimated from calculated van der Waals densities. Relative normalized density means density normalized to the value obtained for hGH without saccharide. All disaccharide containing systems contained sodium phosphate buffer, but the density measurement for hGH alone did not contain buffer. Thus, the value of density for hGH (zero disaccharide) was evaluated from the measured value for pure hGH (1.282) and handbook literature values for density of phosphate salts to give the value for zero disaccharide used in the plot (1.327). Error bars indicated standard errors evaluated from density errors using propagation of errors. Error estimate in the van der Waals density is about 2.5%. ANOVA comparing sucrose with trehalose systems gave a P value of 0.20 (Tukey’s HSD).