Hampton Screen

[Bob Cudney]

>Are there other crystallographers out there who have problems reproducing
>protein crystals which have been obtained using Hampton Screen solutions??
>We have repeatedly encountered problems when screening around the stated
>components of a solution. Is this a general problem or is it dependent on
>our "handling" of the solutions?

Hampton Research uses Fluka as the OEM chemical vendor in all of the 
crystallization screening kits save for magnesium formate (Pfaltz & Bauer).  The 
highest purity available reagent is utilized.  If you use an alternate vendor, 
be sure the chemical is at least ACS grade.  Keep in mind that Fluka offers many 
reagents in a Biochemica Microselect grade which is more pure than ACS grade.  
No, Hampton Research does not have an investment in Fluka.  We have simply found 
there quality to be high and very, very consistent.

Specialized reagents such as chemicals used in the Hampton Research Detergent 
and Additive Screens are sourced from the chemical manufacture who Hampton 
Research  found to offer the "best" (pure and consistent) reagent for 
crystallization.  Again, please contact Hampton Research for details.  Do not 
assume everything is from Fluka.  Please check with us before spending your 
money on chemicals.

Reproducibility problems can be traced to several items including:

1) Using a reagent from an alternate vendor.  This is most usually a problem 
with PEG and MPD but can sometimes be a problem with buffers and rarely with 
salts.

2) Be sure the formulation is the same. Please feel free to contact Hampton 
Research for formulation details on any kit.

3) Technique used in the preparation of the reagents.  Always use analytical 
methods, being especially careful when weighing or measuring volume.  For 
volumes, markings on centrifuge tubes are not good enough, nor are beakers or 
even graduated cylinders.  Errors can range from 3 to 15% with these vessels.  
When possible use gravimetric methods and volumetric methods.

4) Be sure pH measurements are recorded at room temperature when reproducing 
Hampton Research reagents.  Be sure the pH probe is accurately calibrated.

5) Be sure to keep volatile reagents covered during formulation.  Evaporation of 
water, acetate, ammonia or volatile organics can lead to end concentration 
variability.

6) How pure is your water?  When was the last time you changed your cartridge?  
Check the pH and conductivity of the water frequently.

There are other considerations beyond those listed above.  Please feel free to 
contact Hampton Research any time you have questions regarding reagent 
formulation.  We keep no secrets and want to be sure you can reproduce those 
crystals!

We hope this helps.

See ya - Bob Cudney - Hampton Research (xtalrox at aol.com)

Hampton Research
25431 Cabot Road, Suite 205
Laguna Hills, CA 92653 USA
Telephone: 714 699 1040  Fax: 714 586 1453
http://www.hamptonresearch.com