Desalting column

Separate excess cystamine and EDC (and reaction by-products) from the modified protein by dialysis or gel filtration using 10 mM sodium phosphate, 0.15M NaCl, pH 7.2. A desalting column may be used for the gel filtration procedure (i.e., Zeba spin columns from Thermo Fisher). 

Purify the modified protein away from excess reagent and reaction by-products by gel filtration using a desalting column or dialysis. 

Purify the derivatized dendrimer using gel filtration (size exclusion chromatography) on a desalting column or through use of ultrafiltration spin-tubes (for G-4 and above). For smaller dendrimers, the derivatives may be purified by repeated precipitation from a meth-anolic solution by addition of ethyl acetate, dioxane, or benzene. The SPDP-dendrimer may be dried by lyophilization (if in water or buffer) or by solvent evaporation in vacuo (if the precipitation method was used). 

Quench the reaction by immediate gel filtration on a desalting column. If a dextran-based resin is used for the chromatography, the support itself will react with sodium periodate to quench excess reagent. Alternatively, N-acetylmethionine may be added to quench the reaction, because the thioether of the methionine side chain will react with periodate to form sulfoxide or sulfone products (Geoghegan and Stroh, 1992). In addition, sodium... 

Quench the oxidation reaction by the addition of at least a 4-fold molar excess of N-acetylmethionine or sodium sulfite over the concentration of periodate in the reaction mixture (e.g., 40mM). Pre-dissolve the quencher in buffer at a higher concentration prior to adding an aliquot of it to the reaction solution. React for 10 minutes. Alternatively, the oxidation reaction may be stopped by the removal of excess periodate by gel filtration using a desalting column. 

To separate unconjugated hapten and formaldehyde from the synthesized conjugate, apply the entire volume of reactants to a desalting column containing a bed volume of at least 10 times the volume of the reaction mixture. PBS, pH 7.2 can be used for the desalting step. The purified conjugate is recovered in the void volume. 

Immediately purify the maleimide-activated protein by applying the reaction mixture to a desalting column. Do not dialyze the solution, since the maleimide activity will be lost over... 

To purify the SATA-modified (strept)avidin use gel filtration on a desalting column or dialyze against 0.1M sodium phosphate, 0.15M NaCl, pH 7.2, containing lOmM EDTA. At this point, the derivative is stable and may be stored under conditions which favor long-term (strept)avidin activity. 

Reversibility of inhibition can be assessed by dialyzing the inhibited enzyme versus buffer, or by passing the inhibited enzyme down a desalting column, or by a dilution procedure. In each case, an uninhibited (control) sample of enzyme should be treated in parallel with the inhibited enzyme sample, as control enzyme activity often changes to some degree as a result of the experimental procedure. 

The columns are here designed specifically for a defined purpose. These columns are easier to use, faster and they require much less resources. Some of the columns include the NAP-25 or PD 10 desalting columns (from Amersham Biosciences), His Tag columns such as Ni-NTA spin column from Qiagen, His Bind from Novagen or His GraviTrap from GE Healthcare. 

Desalt the sample using a Hi-trap desalting column. 

Desalting column 7. Pool appropriate fractions together. 

Method 1. Dissolve DNA in an appropriate volume (0.5-1.0 ml) of solution A. 8. Pass through a desalting column. 

Disposable desalting columns or a gel-filtration column. Amicon GH-25 and Sephadex G-25 or the equivalent, equilibrated with PBS or buffer of choice... 

Using gravity flow, pass the myoglobin solution over a Sephadex G-25 desalting column to remove excess hydrosulfite. 

Purify the ligation mix as thoroughly as possible. For efficient transformation, it is important to remove all the ions by passing through a desalting column or by dialysis. Concentrate the DNA to approximately 1 pg pL 1. 

Immediately purify the maleimide-activated HRP away from excess cross-linker and reaction by-products by gel filtration on a desalting column (Sephadex G-25 or the equivalent). Use 0.1 M sodium phosphate, 0.15 M NaCl, pH 7.2, as the chromatography buffer. HRP can be observed visually as it flows through the column due to the color of its heme ring. Pool the fractions containing the HRP peak. After elution, adjust the HRP concentration to 10 mg/ml for the conjuga-... 

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