Deep well blocks (1 mL/condition)

The PurePEGs screen comprises 96 conditions for each of which the precipitant is a smear of purified PEGs, ranging from 300 to 8000 in molecular weight. 

 

Features:


  • 96 individual crystallization conditions
  • Ultra pure PEGs - USP grade
  • Polydisperse PEG cocktail – 5 PEGs ranging from 300 to 8000 in each condition
  • Effective forvapor diffusion, but optimized for the Crystal Former
  •  Highest control of manufacturing impurities in the PEGs
  •  Available as tube or deep-well block formats

 

Rationale:

Many of the most successful crystallization conditions are a combination of PEG and salts adjusted to a particular pH.  However, in an initial sparse matrix screen, sample the vast space of different salts versus different molecular weight PEGs, at a range of pH, is a challenging prospect. There is evidence to suggest that protein crystallization hits obtained using a particular PEG can be repeated when using alternative PEGS or mixtures of PEGs.  Consequently, a more rational screening strategy should use mixtures of PEG rather than individual components. 

 

Why use USP grade PEGs?

Additionally, the pH of various sparse matrix screen solutions has been observed to significantly differ from what can be inferred from the precipitant composition.  Since most crystallization screens are manufactured by simply adding individual pre-formulated components to generate a final solution, without adjusting or measuring the pH of the final solution, there are bound to be significant discrepancies between the expected and actual pH of the precipitant condition.  Particularly for conditions containing technical grade PEG, variable concentrations of sodium sulfate, sodium hydroxide or sulfuric acid, will affect the pH and the sales in the final solution.   As a consequence, protein crystallographers trying to optimize a crystallization hit from such a condition may have an incorrect starting point for their efforts. 

To address these issues, the PurePEGs screen contains USP grade, highly purified PEG components.  

 

Can I use these in vapor diffusion trials?

Yes! The PurePEGs screen has been formulated for use in both liquid-liquid diffusion and vapor diffusion.  For the latter, the use of a PEG cocktail, or smear, as the precipitating reagent permits reduction in the number of PEG-based conditions needed to identify an initial crystallization hit.  In the former, the cocktail permits the exploration of broad and complex PEG-based gradients along the Crystal Former capillary.

 

PurePEGs Screen
SKU
50% PurePEGs Cocktail - 100 mL

Optimize your crystals from the PurePEGs crystallization screen with the PurePEGs cocktail. This... Read more

PurePEG-refill $89.00
PurePEGs-96 Crystallization Screen Deep Well Block

The PurePEGs-96 Crystallization Screen features conditions that each... Read more

PP96-1mL $230.00
PurePEGSs-96 Crystallization Screen 10 mL format

The PurePEGs-96 Crystallization Screen features conditions that each contain a mixture of purified... Read more
PP96-10mL $750.00
Well Condition Suite # Volume Sell price Add to cart form
MCSG1-1 A1 1 MCSG-1 100mL $83.00
MCSG1-10 A10 10 MCSG-1 100mL $83.00
MCSG1-11 A11 11 MCSG-1 100mL $83.00
MCSG1-12 A12 12 MCSG-1 100mL $83.00
MCSG1-13 B1 13 MCSG-1 100mL $83.00
MCSG1-14 B2 14 MCSG-1 100mL $83.00
MCSG1-15 B3 15 MCSG-1 100mL $83.00
MCSG1-16 B4 16 MCSG-1 100mL $83.00
MCSG1-17 B5 17 MCSG-1 100mL $83.00
MCSG1-18 B6 18 MCSG-1 100mL $83.00
MCSG1-19 B7 19 MCSG-1 100mL $83.00
MCSG1-2 A2 2 MCSG-1 100mL $83.00
MCSG1-20 B8 20 MCSG-1 100mL $83.00
MCSG1-21 B9 21 MCSG-1 100mL $83.00
MCSG1-22 B10 22 MCSG-1 100mL $83.00
MCSG1-23 B11 23 MCSG-1 100mL $83.00
MCSG1-24 B12 24 MCSG-1 100mL $83.00
MCSG1-25 C1 25 MCSG-1 100mL $83.00
MCSG1-26 C2 26 MCSG-1 100mL $83.00
MCSG1-27 C3 27 MCSG-1 100mL $83.00

What is the advantage of using a PEG cocktail screen as opposed to traditional PEG/Ion screen?

There is evidence to suggest that protein crystallization hits obtained using a particular PEG can be repeated when using alternative PEGS or mixtures of PEGs. Consequently, a more rational screening strategy should use mixtures of PEG rather than individual components to cover a broader crystallization space in a fewer number of conditions. The smear could be deconvoluted into the component PEGs, if that becomes necessary for crystal optimization. Finally, each conditions has a final pH value reported, which is often quite different from the buffer pH value. This gives researchers a more accurate starting point for their crystal optimization trials.

What is the composition of the PurePEG smear?

Each condition of PurePEG screen contains 22.5% of a PurePEG smear mix, with a 4.5% of each of the following USP-grade PEGs: 300, 400, 1000, 4000 and 8000. The cocktail is available as 50% stock for optimization experiments.

Why do you use USP grade PEGs?

Technical grade PEG are known to contain variable concentrations of manufacturing byproducts, like sodium sulfate, sodium hydroxide or sulfuric acid. The affect the pH and the salt composition of the final crystallization condition. As a consequence, protein crystallographers trying to optimize a crystallization hit from such a condition may have an incorrect starting point for their efforts. We recommend using USP-grade PEG reagents for reproducing and optimizing crystals hits in PurePEG screen.

I’d like to optimize a condition from a PurePEG crystallization condition, how do I go about this?

You can purchase the individual, USP grade PEG components directly from Microlytic, as well as 50% PurePEG cocktail. Crystal hits can be optimized by setting up a grid screen around the initial condition, varying the concentration of the PurePEG cocktail along one axis, like you would with any other reagent. Since the concentration gradient is explored in each capillary, the grid screen does not need to be as fine as the one typically devised for hit optimization in VD. However, optimization of crystallization hits from the PurePEG screen is not necessarily contingent on use of the PEG cocktail. Users may utilize small, medium and large MW PEGs to do three parallel grid screens around the initial hit. For many PEG-containing conditions, the identity of the PEG is not absolute for crystal reproducibility. PEG compounds can often be substituted for one another, though a wider range of PEG concentrations should be explored. The major consideration for the reproducibility of crystal hit from the PurePEG screen is the PEG purity. Most PEG compounds utilized for crystallization have not traditionally been USP grade. As such, the presence of contaminants in low PEG grades may hinder the reproducibility of crystals.

What formats does the PurePEG screen come in?

PurePEG screen is available in the 2 mL deep well block format with 1.0 mL of each condition. The blocks are heat-sealed for safer transportation and longer storage. The tube format consists of 15 mL comical tubes containing 10 mL of screening solutions. The tubes racks are shrink-wrapped for safer transportation.

Do you have production reports available?

Yes, lot-specific production reports are available for the PurePEG-96 screen. Simply provide the Lot # from your block or tube set to support@microlytic.com and you will receive a detailed production report including the lots of the individual chemicals used within 24-48 hours.

Can I buy optimization reagents for the PurePEG screen?

50% stock of PurePEG cocktail is available in 100 mL volumes. We also offer all individual USP grade PEGs as liquid or dry stocks. All other component chemicals are also available in the same high purity grade used in the PurePEG screen manufacturing.