Jim Pflugraph (Rigaku): I always try sugars for everything.  There is a cryocrystallography webinar at rigaku.com with embedded videos on how to do this.  50% to 100% saturated sugar (sucrose, glucose, trehalose, sorbitol, et al.) in reservoir buffer is usually what I try.

Japan AEA: Cryoprotectant Database

Artem Evdokimov: Cryoprotection of Delicate Crystals

Introduction

The procedure below summarizes one of the approaches to cryoprotection commonly employed in our lab. This approach worked for me on many occasions, but obviously I cannot promise that it works with every crystal, all the time.

I would like to mention that this is not the easiest approach, and certainly not the first that we try on a new crystal (I usually start with 20-25% ethylene glycol in crystal mother liquor; this seems to be satisfactory for at least 50% of crystals I worked with). However, if you have a few crystals to spare, and the simpler things did not pan out, this method is worth trying.

This approach has been hashed out during the late-night hours at various synchrotron beam lines, and has not been put to a rigorous statistical test, so it’s not likely that this kind of semi-anecdotal stuff will see the light of day as a real paper. Many colleagues and friends have contributed through discussion, for which I am very grateful. It is likely that someone has described similar, if not the same considerations before. If this is the case, I would appreciate the reference so that I could give proper credit for earlier work.

I am always most grateful for comments, suggestions, or anecdotes of success/failure. (Click for the FULL ARTICLE)