Half-maximum Points Research Articles

乳酸菌による蛋白質の榮養價の測定に就て(豫報)

The authors have studied so called “lactic acid value” of various protein such as egg albumin, casein, gelatin, glutenine, etc. using Lact. arabinosus, Leuc, mesenteroides, Lact. casei, Lact. fermenti, and Str. faecalis, as test organisms. The lactic acid value were measured according to ordinary bio-assay method(1) with acid and pancreatin-hydrlysates of the above proteins, the basal medium being shown in Table 1, and expressed by maximal acid production and tan θ=V/C, where V indicates number of c. c. of 0.05 N NaOH at the half maximum point and C the concentration of the protein in per cent. The results are shown in Table 2. It is clear from these results that under the conditions so far investigated the lactic acid values of various proteins vary according to the species of the testorganisms and this fact shows not only the complicated relationships in the amino acid requirements of individual lactic acid bacteria, but also the fact that such method as adopted by the authors may properly be used in determining the nutritive values of raw materials for organisms used in the fermentation industries. If we can find either a complete parallelism between the lactic acid value and the ordinary biological value or nutritive equivalence between various proteins through proper selection of the test orgamism, it may be possible to determine the nutritive values of proteins for animals through a microbiological way. The comparison between the “lactic acid values” and the biological values is shown in Table 3 where Str. faecalis is proved to be comparatively fit for the purpose. The authors are deeply indebted to Dr. Raper and Dr. Smith of the N. R. R. L. for granting us the test organisms.

Direct Measurement of X-Ray Mass Scattering Coefficient

The mass scattering coefficients for Li, B, C, ${\mathrm{H}}_{2}$O and Na at wave-lengths $\ensuremath{\lambda}.32$,.43,.54,.66,.79A were measured directly by collecting the scattered radiation in an ionization chamber surrounding the scatterer, and comparing its intensity with that of a portion of the primary beam going through an auxiliary ionization chamber of equal length along the ray path. The primary beam consisted of the continuous radiation from a Coolidge tungsten tube, filtered through Al and Cu until the spectral width between the half-maximum intensity points was about 25 percent of the mean wave-length. Corrections were made for internal absorption in the scatterer and for the increased absorption of the scattered beam in the ionization chamber due to the Compton effect. The uncertainty in these corrections forms the chief limitation on the accuracy of the measurement. The values of mass scattering coefficient determined are tabulated. The scattering coefficient in all cases starts, for short wave-lengths, below the value computed from Thomson's formula, and slowly increases for longer wave-lengths. For all substances but boron it finally crosses the Thomson value because of gradual entering in of excess scattering.