Mass balancing, amino acids

The proximate composition of canola/rapeseed varies among varieties as a result of both genetic makeup and growing conditions. As summarized in Table 4.3 [4], the oil content of canola is about twice that of soyabeans and contains much more fibre than soyabeans. The protein content of oil-free canola meal is only slightly lower than that of soyabeans. Canola is processed primarily for its oil, which makes up some 40% of the seed mass. It has an ideal fatty acid composition for human consumption, with a linoleic-to-linolenic acid ratio of approximately 2. After oil removal, the meal contains more than 40% protein with well-balanced amino acid composition. The essential amino acid composition, given in Table 4.4, indicates that canola protein is superior... 

The frustrating and sometimes capricious nature of simple reactions of 2-amino-4(5H)-oxazolones is exemplified in the following reports. Ramsh and co-workers acetylated 68 with acetyl chloride in benzene but isolated both a poor yield and a poor mass balance of 131 together with dehydroacetic acid 132. Attempts to transaminate 131 with diethylamine in the absence of a solvent or with aniline in benzene failed. The authors recovered 68, which is in stark contrast to an earlier report from Hansen and Masch that acetylation of 68 with acetic anhydride gave 131 in 87% yield. In addition, these same authors reported that reaction of 131 with diethylamine at room temperature gave 134 in excellent yield (Scheme 6.35). 

It has been demonstrated that ILMs are suitable for qualitative and quantitative analyses of low-molecular weight compounds of biological interest, for example, carbohydrates, vitamins and amino acids [38], and glycolipids [40]. ILMs were further used for fhe direct analysis of alkaloids, anesthetics and antibiotics, separated by thin-layer chromatography (TLC) [46]. For this purpose, the ILM was spotted onto the fractions on the TLC-plates and the complete plate was measured in MALDI MS without the need for additional pretreatment of the TLC-samples. The mass deviation inherently caused by the inhomogeneous surface of fhe TLC-plafe was balanced by using the... 

Extrinsic stabilization from low-molecular-mass "thermoprotectants." The intrinsic stability of a protein reflects selection for an amino acid sequence that confers on the protein the appropriate balance between rigidity and flexibility that is required for physiological function under the thermal conditions facing the organism. This being said, the stability of the protein in vivo may be modulated by extrinsic factors, including pH, which varies with temperature, and low-molecular-mass organic osmolytes, whose concentrations may be tern-... 

ADME Since metabolism and formation of active metabolites are not a concern for unmodified biopharmaceuticals, mass balance studies are uninformative. Tissue concentration of radioactivity using radioactive proteins is also difficult to interpret due to unstable radiolabel linkage, rapid in vivo catabolism, and recycling of radiolabeled amino acids into non-drug-related proteins/peptides. 

The pharmacokinetic evaluation of biopharmaceuticals is generally simplified by the usual metabolism of products to small peptides and to amino acids, and thus classical biotransformation and metabolism studies are rarely necessary. Routine studies to assess mass balance are not useful. However, both single- and multiple-dose toxicokinetic data are essential in safety pharmacology asessments, and these can be complicated by two factors (1) biphasic clearance with a saturable, initial, receptor-dependent clearance phase, which may cause nonlinearity in dose-exposure relationships and doseresponses [14] and (2) antibody production against an antigenic biopharmaceutical that can alter clearance or activity in more chronic repeat-dose safety studies in the preclinical model. 

Because of the catabolism of proteins to (mostly) endogenous amino acids, classical biotransformation studies as performed for small molecules are not needed. Additionally, limitations of current analytical methods to detect and distinguish metabolites and the putative lack of pharmacological or toxicological activity of the metabolites, remain obstacles. Similarly mass balance studies... 

When peptides with subtle differences in hydrophobicity are being separated, nonionic surfactants may provide a better balance between the electrostatic and hydrophobic forces influencing the separation. Polyoxyethylene-10 (20 mM) has been found useful for separating two analogues of growth hormone-releasing peptide (composed of six amino acids) with the same mass-to-charge ratio. 

As the model suggests, the dietary need for amino acids is determined by the rates of depletion of the free amino acid pool by oxidation or synthesis of protein. During steady state conditions, the contribution to the free pool from dietary intake and protein breakdown should be exactly balanced by the flux out of the pool to synthesis and oxidation. Any condition that increases deposition of protein in the body or the rate of amino acid oxidation should produce an increased need for protein. For example, muscle hypertrophy is dependent on a positive balance of the protein turnover process. If synthesis of protein exceeds the catabolism of protein, then muscle mass will increase and the free amino acid pool would be depleted. Thus, a net increase in protein requires an increase in intake or a decrease in oxidation. Likewise, the same arguments hold for an increase in oxidation of amino acids. 

The mathematical treatment of FMC data can be accomplished by standard procedures via the solution of mass balance equations, on condition that the data were converted to reaction rate data with Eq. (21). As mentioned above, this requires the determination of the transformation parameter a. Two approaches based on calibration were developed and tested. In the first approach, thermometric signals are combined with the absolute activity of IMB, which had been determined by a separate measurement using an independent analytical technique. Figure 5 shows a calibration for the cephalosporin C transformation catalyzed by D-amino acid oxidase. The activity of the IMB was determined by the reaction rate measurement in a stirred-tank batch reactor. The reaction rate was determined as the initial rate of consumption of cephalosporin C monitored by HPLC analysis. The thermometric response was measured for each IMB packed in the FMC column, and plotted against the corresponding reaction rate. From the calibration results shown in Fig. 5 it can be concluded, independently of the type of immobilized biocatalyst, that the data fall to the same line and that there is a linear correlation between the heat response and the activity of the catalyst packed in the column. The transformation parameter a was determined from... 

In spite of usefulness of the simplification obtained by decreasing the experimental substrate concentration, many studies are aimed at the investigation of kinetic properties of immobilized biocatalysts within broader concentration ranges. In a previous paper [29], cells of Escherichia coli with penicillin acylase activity were immobilized by entrapment in calcium pectate gel and tested on the transformation of penicillin G to 6-amino penicillanic acid. Figure 9 shows experimental data from a microcalorimetric investigation of the penicillin G transformation in steady state. As appreciable particle-mass transfer was expected, the mathematical model that includes particle-mass balance was used. 

We are going to consider the cell as a reactor The nutrient com steep liquor enters the cell of the microorganism PenicUlium chrysogenum and is decomposed to form such products as amino acids. RNA. and DNA. Write an unsteady mass balance on (a) the com steep liquor, (b) RNA. and (c) pencil-lin. Assume the cell is well mixed and that RNA remains inside the cell. 

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