G-Biosciences’ ML (Modified Lowry) Protein Assay is based on the widely cited protein assay by Lowry et. al. (1951). 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).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 CL (Compatible Lowry) Protein Assay is available for samples containingreducing agents (such as dithiothreitol (DTT), ß-mercaptoethanol and TCEP) and a wide variety of commonly used laboratory agents that are known to interfere with Lowry’s protein assays (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
- 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 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.
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