Nitrogen measurement in biological fluids and bone by an automatic Dumas technique

Total Protein Content Determination of Microalgal Biomass by Elemental Nitrogen Analysis and a Dedicated Nitrogen-to-Protein Conversion Factor

Accurately determining protein content is important in the valorization of algal biomass in food, feed, and fuel markets, where these values are used for component balance calculations. Conversion of elemental nitrogen to protein is a well-accepted and widely practiced method, but depends on developing an applicable nitrogen-to-protein conversion factor. The methodology reported here covers the quantitative assessment of the total nitrogen content of algal biomass and a description of the methodology that underpins the accurate de novo calculation of a dedicated nitrogen-to-protein conversion factor.

Algal biomass constituent analysis: method uncertainties and investigation of the underlying measuring chemistries

Algal biomass compositional analysis data form the basis of a large number of techno-economic process analysis models that are used to investigate and compare different processes in algal biofuels production. However, the analytical methods used to generate these data are far from standardized. This work investigated the applicability of common methods for rapid chemical analysis of biomass samples with respect to accuracy and precision. This study measured lipids, protein, carbohydrates, ash, and moisture of a single algal biomass sample at 3 institutions by 8 independent researchers over 12 separate workdays. Results show statistically significant differences in the results from a given analytical method among laboratories but not between analysts at individual laboratories, suggesting consistent training is a critical issue for empirical analytical methods. Significantly different results from multiple lipid and protein measurements were found to be due to different measurement chemistries. We identified a set of compositional analysis procedures that are in best agreement with data obtained by more advanced analytical procedures. The methods described here and used for the round robin experiment do not require specialized instrumentation, and with detailed analytical documentation, the differences between laboratories can be markedly reduced.

Metabolic effects of propranolol in thyrotoxicosis. I. Nitrogen, calcium, and hydroxyproline

The effect of propranolol on the hypermetabolism of thyrotoxicosis was investigated in eight subjects with diffuse toxic goiter. After equilibration on a constant nitrogen, calcium, and hydroxproline intake, nitrogen balance was determined before and during propranolol therapy prior to subtotal thyroidectomy and compared to similar data obtained in seven of the patients following surgically induced euthyroidism. Propranolol administration was associated with clinical amelioration and a rapid, statistically significant, improvement in nitrogen retention. A slight additional improvement in retention was noted in the postoperative euthyroid state. Oxygen consumption, measured serially in four patients, was not significantly changed by propranolol. Urinary loss of calcium, phosphorus, and hydroxyproline was unaffected by propranolol, but excretion of these substances was sharply reduced in the subjects restudied postoperatively. These data offer a evidence of a previously unreported nitrogen sparing effect of oral propranolol during its short-term administration in thyrotoxic man.