G-Biosciences’ CL (Compatible Lowry) Protein Assay is based on the widely cited protein assay by Lowry et. al. (1951). The CL Protein Assay improves upon the traditional Lowry method to be compatible with common laboratory agents known to interfere with Lowry protein assays such as reducing agents (dithiothreitol (DTT), ß-mercaptoethanol and TCEP), detergents, chelating agents, amines, sugars, strong chaotropic buffers, salts, drugs, antibiotics, cobalt and other common laboratory agents (see tables 1 and 2). The CL Protein Assay uses G-Biosciences’ proprietary Universal Protein Precipitating Agent (UPPA™). The UPPA agent cleans the protein samples from interfering agents prior to performing colorimetric reaction.The assay is supplied with either traditional bovine serum albumin (BSA) protein stand ard, pre-diluted BSA protein stand ards, non animal protein stand ard or bovine? globulin protein stand ard.
A ML (Modified Lowry) Protein Assay is available for detergent containing samples without reducing agents.The ML Protein Assay is compatible with a wide variety of detergents used in protein research in addition to other common reagents such as EDTA and Tris(see tables 1 and 2).
Table-1: A selection of compounds and their maximum concentrations compatible with the ML and CL Protein Assay.| Reagent | ML Protein Assay | CL Protein Assay |
| Amino Acids | Compatible | - |
| Ammonium Sulfate | 0.5M | 40% |
| β-Mercaptoethanol | X | 5%, 15%* |
| Brij® 35 | 1% | 1% |
| Calcium Chloride | 0.05M | - |
| CHAPS | 1% | 4% |
| CHAPSO | 1% | 1% |
| CTAB | - | 1M |
| Deoxycholate | 1% | - |
| Digitonin | 0.3% | - |
| DTT | 0.001M | 0.1M, 0.35M* |
| EDTA | 0.025M | 0.1M |
| Glycerol | - | 30% |
| Guanidine.HCl | 0.4M | 6M |
| Guanidine Thiocynate | - | 6M |
| HEPES | - | 0.1M |
| Hydrochloric Acid | 0.5M | - |
| Imidazole | - | 0.5M |
| Iodoacetamide | - | 15mM |
| Laemmli Buffer (w/5% β-Mercaptoethanol) | - | Compatible |
| NP-40 | 2% | - |
| Octaethyleneglycol dodecyl ether | 0.2% | - |
| Octyl Glucoside | 1% | - |
| Phosphate Buffer | - | 0.2M |
| Sarcosyl | - | 1% |
| SDS | 10% | - |
| Sodium Azide | 0.05% | 0.1M |
| Sodium Chloride | - | 0.5M |
| Sodium Hydroxide | 0.5M | 2.5M |
| Sucrose | - | 30% |
| TCEP | - | 15mM |
| Thesit® | 1% | 2% |
| Thiourea | - | 2M |
| Tributylphosphine (TBP) | 0.002M | - |
| Tris (pH 8) | 0.1M | 0.5M |
| Triton® X-100 | 1% | 3% |
| Triton® X-114 | 1% | 3% |
| Tween® 20 | 1% | 2% |
| Urea | 4M | 8M |
| Zwittergent® 3-12 | - | 1.5M |
-, not tested; X, not compatible; *, two washes (optional).
Table 2: ML & CL Protein Assay are compatible with strong chaotropic extraction buffers
| Buffer Composition |
| 4M Urea, 1% SDS, 10mM EDTA, 0.8% β-Mercaptoethanol |
| 6M Urea, 2M Thiourea, 4% CHAPS |
| 6M Urea, 2M Thiourea, 4% NP-40 |
| 1% Sarcosyl, 0.8 β-Mercaptoethanol, 4M Guanidine Thiocyanate, 10mM EDTA |
| 6M Urea, 2M Thiourea, 2% CHAPS, 2% ND SB 201 |
| 6M Urea, 2M Thiourea, 2% CHAPS, 2% SB 2 10 |
Features- Protein quantitation in the presence of detergents and reducing agents
- Quick 15 minute incubation
- Increased color stability (color will not change more than 5% in 1 hour or 10% in 2 hours)
- Linear response 0.2 –1.5 mg/ml
- One simple protocol without cumbersome sample preparationor buffer exchange steps
- Convenient kit provides all necessary reagents for 250 stand ard (5ml) assays or 1000 microtube (1.5-2 ml) assays
Applications?- Estimate protein during protein purification, electrophoresis, cell biology, molecular biology, and other research applications.
- Suitable for protein samples containing common laboratory agents, such as reducing agents, chelating agents (EDTA), detergents, amines (Tris), sugars and many other agents.
- Suitable for samples containing chaotropic agents such as urea, thiourea, guanidine hydrochloride, guanidine thiocyanate, ammonium sulfate, drugs, antibiotics, cobalt, and numerous other agents and extraction buffers.
- Suitable for determination of protein concentration in cellular fractions, tissue & cell lysates and chromatography purification fractions.