Salts and buffers

These will be dealt with in Chapters 5 and 6 here only the definitions will be given  

Type of solution Example Comment Acidity/basicity 

Classify the following solutions into strong acid, buffer etc  

Parts (e) and (f) require a calculation of the number of mol in each solution. Thereafter the 

Care must be taken with the units since concentration is usually given as mol dm then the volume must be given in dm. In this question volumes are given as, e.g. 10 cm = 10 X 10-3 dm  

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If unidentified peaks are detected the stability of the protein under the chromatographic conditions should be checked. In all analytical investigations of proteins on SEC columns it is desirable to be able to monitor the eluted peaks at a very high sensitivity of the ultraviolet detector. Therefore, very pure (analytical grade) salts and buffers should be used. 

Nonionic samples can generally be analyzed vithout an adjustment of the pH or the salt concentration of the mobile phase. However, many typical samples are ionic or ionogenic. Under these circumstances, the addition of salt to the mobile phase is often required to prevent exclusion effects that are not related to the size of the analyte molecule. Ultrahydrogel columns are compatible with a broad range of salt and buffer solutions. Recommended compositions can be found in Table 11.6, but a broader range of buffers can be used. 

Aqueous GPC can also be semiprepped in manner just like nonaqueous GPC. In this case one must consider carefully the buffers, salts, and biocides used in the eluant. If the fractions are destined for nuclear magnetic resonance experiments it will be imperative to either reduce the salt concentration in the eluant or remove salt after the initial fractionation. Likewise, if the collected samples are destined for infrared (IR) analysis, it is important to choose salts and buffers that have good IR transparency in the wavenumber ranges of interest. 

This problem can be circumvented by concentrating the sample, but care should be taken to ensure that salt and buffer concentrations are not too high for the technique. Other detection systems can be used, in particular electrochemical detectors... 

In these ionization procedures, the sample is split up into individual molecules and ionised under as gentle conditions as possible. Ideally, the sample should be dissolved in pure solvent, but this is often not possible since, for most biological macromolecules, salt and buffer solutions are needed to ensure the solubility and structural integrity of the sample. Since the ionic species generated from salts and buffers in the sample can interfere with the mass spectrum produced these need to be kept as dilute as possible. 

Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) routinely gives MW values with an accuracy of 0.1% or better, and has become increasingly popular for the mass measurement of biopolymers [1]. The technique is simple, rugged, has a mass range in excess of 200,000 Da, and is extremely sensitive, requiring low nanomole to picomole amounts of material. Additionally, the technique is relatively insensitive to the presence of various salts and buffers that are often associated with the isolation of biomolecules. 

An additional advantage to desorbing proteins directly from binding membranes is the ability to wash bound proteins free of contaminates that typically suppress ionization [3]. Although MALDI is relatively tolerant of the presence of salts and buffers, it is extremely susceptible to the presence of surfactants such as sodium dodecyl sulfate (SDS), with spectral degradation... 

In this study, we used matrix-assisted laser desorption ionization /Mass Spectrometry (MALDI/MS) to identify the peptides released from gastric parietal cell microsomes. MALDI, because of its sensitivity and relative tolerance to the presence of salts and buffers was examined for the analysis of unfractionated proteolytic digests (9, 10). MALDI with post-source decay (PSD) analysis was used to obtain sequence information on peptides even in crude digestion mixtures. Our strategy (Figure 1) consisted of proteolysis of intact vesicles, centrifugation at high speeds to separate membrane bound and soluble fractions and analysis of the mixture of released peptides by MALDI/MS. In addition, to increase the... 

Besides the improvements in sensitivity and the reduction of sample consumption, nano-ESl shows several other advantages over conventional ESI [4]. Stable performance of ESl-MS with aqueous samples is easier to achieve. There is greater tolerance towards salts and buffers, almost allowing physiological conditions to be used, and enhanced performance for certain compound classes, e.g., noncovalent protein complexes. These effects can be explained in terms of the reduced number of fissions to off-spring droplets and improved surface-to-volume ratio, resulting from the smaller initial droplet size in nano-ESl relative to conventional ESI. 

With a proper choice of mobile phase (aqueous or nonaqueous), many commercially columns are available for SEC of PVP and VP-based copolymers. Mobile-phase modifiers (such as methanol, salt, and buffer) are normally required to eliminate interactions with columns. A single linear or mixed-bed column has been found to provide good separation of PVP and VP-based copolymers with a molecular weight range of from a few thousands to several millions. In general, the aqueous SEC system has better long-term stability and provides better separation than the nonaqueous SEC system, especially at the low-molecular-weight end. Hydroxylated methyl-methacrylate-type columns and water-methanol mobile phase (50 ... 

G3. Carry, F. J., Serum cholinesterase variants Examination of several differential inhibitors, salts, and buffers used to measure enzyme activity. Clin. Chem. 17,183-191 (1971). 

All salts and buffer components, as well as poly-D,L-lysine (PL), CBZ-protected PL, diethylene triamine penta-acetic acid (DTPA) and its anhydrides, water-soluble carbodiimide (l-ethyl-3-(dimethylaminopropyl)-carbodiimide, EDC), (SPDP), SMCC, dithiothreithol, succinic anhydride, trinitrobenzene sulfonic acid, triethylamine, bovine serum albumin (BSA), and IV-hydroxy sulfo-succinimide (HSSI) are available from Sigma (St. Louis, MO). 

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