Composition and Stoichiometry

Unlike the interstitial monocarbides, MC,, where C is never 1, the interstitial mononitrides, MN,, can have a composition where x 1. In substoichiometric compositions (x 1), the sublattice of nitrogen is predominantly deficient while at hyperstoichiometric compositions (x 1), the metal lattice is predominantly deficient. The lattice parameter is at a maximum at stoichiometry. Even at stoichiometry, a substantial fiaction of both nitrogen and metal sites are usually vacant. 

---

Mendel DB, Orti E. (1988) Isoform composition and stoichiometry of the approx 90-kDa heat shock protein associated with glucocorticoid receptors. J Biol Chem. 263, 6695-6702. 

Among the analytical methods presently used for the characterization of natural and synthetic peptides and proteins, the primary value of amino acid analysis is the determination of absolute peptide and protein content in solids and solutions and the quantitation of their amino acid composition and stoichiometry. It involves two steps, i.e. complete hydrolysis of peptides and proteins, followed by photometric determination of the released amino adds. The steps are laborious and time-consuming, and there is a continuous need for improvement of the techniques to increase precision and sensitivity. 

Some laboratories do not have access to mass spectrometric analysis, but the number is fewer as the cost for this type of instrumentation is decreasing. It is suggested that these laboratories utilize amino acid analysis due to reduced cost and rapid turnaround. Peptide composition and stoichiometry can be determined, the technique is highly reproducible, and can be used to monitor cycle-to-cycle coupling efficiency. However, not all amino acids are recovered quantitatively. Cys and Trp are totally destroyed and must be quantitated using distinctly different hydrolysis procedures. Ser and Thr can be partially destroyed. Some laboratories perform amino acid analysis in addition to mass spectrometric analysis in order to assure peptide composition, stoichiometry, and quantity (see also Sections 7.3, 7.3.1 and 7.3.2). 

The adsorption mechanisms depend on the composition and stoichiometry of the alumina surface slightly different spectra are obtained for silanes adsorbed onto plasma and thermal oxides [4]. 

Elemental analysis Small angle x-ray scattering Chemical composition and stoichiometry Oligomer shape and size 50, 52... 

Pearson s classification is insensitive to both chemical compositions and stoichiometries of metallic alloys. It is quite useful because all known intermetallic crystal structures are grouped according to their structural symbols, which are quite simple. Thus, once the symmetry and the content of the unit cell of a new alloy phase have been established, it only makes sense to search for potentially isostructural compounds among those that have identical Pearson s symbols. 

Methods to distinguish polymorphs are shown in Table 11.3. Byrn [31] suggests that a combination of methods be used to characterize critical solids two for identifying the phase, or morphic state, and two for securing the composition and stoichiometry. 

The above formulation also yields a simple constant for a given input composition and stoichiometry as long as all the products are the result of parallel primary reactions and conversion is carried out at isothermal conditions. Problems in using this more elaborate formulation for TSR studies become obvious as soon as we consider the case where products are formed in the same set of parallel reactions but at different temperatures. The factor that causes difficulty in the case of a TSR is the variation in selectivity for the parallel processes as temperature is ramped. 

While it is believed that the high-order structure of the receptor supramolecular complex has a role in chemotactic signaling, the composition and stoichiometry of the five different MCPs within these receptor supramolecular complexes are not known. If the seven-dimer model [427] is correct, the supramolecular complexes must differ from each other with respect to their MCP compositions. This is because the low-abundance receptors must interact with the high-abundance ones for their normal function [411, 422] and for being a part of the cluster [449]. Had the MCP compositions in all the receptor supramolecular complexes been the same, each complex should have been composed of at least 19-20 receptor dimers according to the known stoichiometry between the different types of MCPs [10-11 Tsr 6 Tar 1 Aer 1 Tap 1 Trg (Table 10)]. If, on the other hand, the lattice model [649] is correct, any MCP combination may be possible. The flexibility that this model... 

Among metals there are differences in composition and stoichiometry of the oxide films. Halides such as chlorides play an important role in the growth and breakdown of passive films. Borates help stabilize the oxide film. Chloride ions cause severe localized corrosion such as pitting. Well-developed pits have high chloride ion concentration and low pH. Pitting can be random and amenable to stochastic (statistical) theory and very sensitive to experimental parameters such as induction time and electrochemical properties, which are difficult to reproduce. Electrochemical noise (EN) can clarify the initial conditions for pit initiation (24). 

Amino acid analysis (AAA) developed by Stein and Moore [67] is the oldest method and is still in use today. Although it has historically been used to determine peptide composition and stoichiometry, it is primarily used today to assess peptide content [68]. For the synthetic peptide chemist this method offers a means of monitoring the progress of a synthesis through analysis of a crude peptide or resin hydrolysate. 

XRD data (Table 1-3, 8) show that, along with apatite, a secondary LaAlOs or LaFeOs phase (2-9 wt.%) is present in samples annealed at different temperatures depending on their composition and stoichiometry [51, 62, 85], For all samples dopants incorporate into the apatite lattice, which is confirmed by IR (Fig. 39) and Al MAS NMR data (Fig. 40). Thus, Al MAS NMR spectra clearly show the presence of Al mainly in tetrahedral coordination. 

Papisov et al. [33] studied the competitetive complexation of two different polymer substrates with PMAA matricies. The authors considered the systems PMAA/PEG/poly(N-vinyl-2-pyrrolidone) (PNVP) and PMAA/PNVP/poly(vinyl alcohol) (PVA) using PNVP and PEG with degrees of polymerization of 360 and 2340 respectively. The complex composition and stoichiometry were determined by centrifugation and followed by elemental analysis. 

---