OptiSol™ Protein Solubility Kits help researchers identify formulations that protect target protein from aggregation, or to solubilize an aggregated protein sample.

OptiSol Protein Solubilization Screening Kit contains a systematically varied array of buffers (from pH 3 to pH 10) and a series of solubility enhancers (salts, amino acids, sugars, polyols, reducing reagents) that enable the determination of conditions under which a particular protein sample is protected from aggregation or can be de-aggregated. A total of 90 different formulations with solubility enhancers can be tested in one single, label-free experiment; the remaining 6 experiments are positive and negative control experiments. The table below lists all reagents in an OptiSol Kit.

The OptiSol Protein Solubility Screening kit can be used for two fundamentally different purposes:
1. Protein Solubility Profiling (Protocol A)

2. Solubilize an Aggregated Protein Sample (Protocol B)

For detailed experimental methods please see Optisol quickstart guide and Optisol manual .

Use Protein Dashboard to assist in visualizing your data!

Click here to download the Protein Dashboard.

The Optisol Protein Solubility Screening kit is compatible with a wide diversity of protein sizes ranging from several kDa to 250 kDa. Filter plates should be selected according to the expected MW of the solubilized protein molecule.

Optisol IPeptides, size < 10 kDa
Optisol IISmall protein molecules > 10 kDa and < 25 kDa
Optisol IIIProtein molecules up to 90 kDa
Optisol IVLarge protein molecules including antibodies and oligomers up to 250 kDa

Will my aggregated protein sample ‘go in solution’ with the OptiSol reagents?

This depends on the nature of the protein aggregate. The only way to find out is by experimental testing – and this is exactly what the OptiSol protein solubility screen does. Test 90 different mild formulations – different pH, salts, polymers, sugars, polyols, detergent, reducing agents. If the protein sample is reversibly aggregated, chances are the OptiSol screen will yield conditions that solubilize the sample.

The formulations employed are rather mild. The goal is to solubilize the aggregate and yield functional protein. Will any aggregated protein samples get solubilized? No, some aggregates just contain ‘dead’ protein. You’ll need SDS or urea for such recalcitrant samples and obtain non-functional protein in return.

How much protein is required to run an OptiSol kit?

The protein concentration will be diluted by 11 times (15 µL/165 µL) in the reaction plate when the protein solution is combined with the formulations. Thus, one has to start with a stock protein solution that is 11 times the final solution concentration in the reaction plate. About 2 mL of protein stock solution is adequate. The required protein concentration depends on the extinction coefficient of the protein and the sensitivity of the protein detection assay. In our laboratory we developed a UV280 method using half-width UV 96-well plate and UV/vis plate reader. In our case, the UV280 absorbance in half-width UV280 wells has to be at least around 0.4 (absolute absorbance units).

OptiPharma vs. OptiSol: Which one I should get?

All ingredients (buffers and additives) in an OptiPharma kit (except 3 control wells) are FDA approved pharmaceutical ingredients. If you have pharmaceutical proteins in any stages of pharmaceutical formulation development, OptiPharma is the one.

OptiSol is applicable to various types of protein work (e.g. pharmaceutical, industrial, food, plant, crystallization work). Most additives in an OptiSol kit are not suitable for pharmaceutical formulations. For example, if you have a crude protein mixture that you want to solubilize, OptiSol is a good choice to start with.