My m values are coming like 237, 286 or 2276 for y=mx+c during bradford assay, due to which my protein concentration is becoming very low. My R square values are around 0.97 or 0.98 or 0.95 and curve is almost straight. I'm using BSA as a standard and by visual inspection, the colour of sample protein is equivalent to 50 ug/ml of BSA colour.
This is hard to answer without seeing the data. But there is a general vulnerability in linear regression: if x does not vary very much then the value of m is unreliable. "not very much" means in comparison to the level of noise.
Make sure that the BSA calibration curve and your protein sample are of the same order (in other words don't extrapolate BSA calibration curve).
Check if the protein you're working on is adapted to bradford reactivity (should contain exposed positively charged residues).
finally, the m values you gave are all without unit. Thus, it is impossible to estimate how bad the slope of your curve could be. As Chris Morris said, hard to help further without additional information.
Sandeep you have to use best fit curve. It is not necessary that linear fit will provide an accurate estimate. If the relationship between concentration and absorbance is best described by a straight line then you can use straight line. If not, you can also use 3 state polynomial equation . Once you have a plot you can easily judge what is best fit for you. It is difficult to provide any quick fix without looking at the actual data.
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