To calculate the protein molecular weight from the provided ESI (Electrospray Ionization) mass spectrum data, we need to identify the various charge states represented in the spectrum. The analysis of charge states can be based on the mass-to-charge ratio (m/z) values given in your list.
Provided m/z Values:
- 893.17
- 942.71
- 1060.44
- 848.54
- 1131.05
- 998.13
- 1211.77
- 808.17
- 1304.89
- 771.50
- 1413.58
- 737.99
- 1542.02
- 707.27
Step 1: Identify Charge States
Charge states can be determined by observing the spacing between the peaks. In ESI spectra, ions of the same species (protein) will appear at different charge states that are typically spaced apart by the unit mass of 1 Da (1 kDa) divided by the charge (z).
Assuming the most abundant ions are singly charged, we can evaluate the most common differences:
- For instance, the difference between closely spaced peaks like:
- 893.17 and 848.54, which suggests charge states (e.g., if 893.17 is +1, then 848.54 might be +2).
Step 2: Calculate "Assumed" Molecular Weight
To calculate the molecular weight of the protein from the charge states, let's select the highest m/z value, which we will assume corresponds to the lowest charge state (most common for proteins):
- The highest value is 1542.02.
If we assume this corresponds to a singly charged ion:
- Molecular Weight (M) = m/z value × charge state
- For a charge state of +1:
- \( M \approx 1542.02 , \text{Da} \)
Step 3: Identify Other Charge States
To evaluate other potential charge states:
- Divide the m/z values by their observed charge. Considering charge states (+1, +2, etc.):
- For example, if 1542.02 corresponds to +2, then the molecular weight would be approximately 3084.04 Da, and you would subtract 1 Da for +1.
Identified Values:
Here’s a proposed list of charge states:
- 1542.02 (assumed +1)
- 1211.77 (assumed +2) → \( M = 1211.77 \times 2 \approx 2423.54 , \text{Da} \)
- 1060.44 (assumed +3) → \( M = 1060.44 \times 3 \approx 3181.32 , \text{Da} \)
- 993.13 (assumed +3) → \( M \approx 2993.39 , \text{Da} \)
- Continue with other values similarly...
Summary of Charge States and Protein Molecular Weight:
The most likely molecular weight for the protein based on the provided data and assuming the highest m/z corresponds to +1 charge state is:
- Molecular Weight ~ 1542.02 Da
Possible charge states identified:
- +4 state corresponds to a molecular weight of approximately 6168.08 Da
Make sure to confirm the charge states based on the spectrum's peak spacing and any additional information on the protein's expected molecular weight.