ML (Modified Lowry) Protein Assay




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 standard, pre-diluted BSA protein standards, non animal protein standard or bovine ÉŁ globulin protein standard.
A CL (Compatible Lowry) Protein Assay is available for samples containing reducing 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 |
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 preparation or buffer exchange steps
- Convenient kit provides all necessary reagents for 250 standard (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.