2. Calculate the protein molecular weight from the spectrum below, and identify all charge state for the below ESI spectrum (5).

Question

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
700
800
900
1000
1100
1200
1300
1400
1500

Answer 1

To calculate the protein molecular weight from the provided ESI (Electrospray Ionization) spectrum data, we first identify the individual peaks and analyze their charge states.

The peaks listed are as follows:

• 893.17
• 942.71
• 1060.44
• 848.54
• 1131.05
• 998.13
• 1211.77
• 808.17
• 1304.89
• 771.50
• 1413.58
• 737.99

Steps to Determine Molecular Weight and Charge States:

1. Identify Charge States: Typically, the spectrum exhibits peaks corresponding to various charge states (z). The molecular weight (MW) of the protein can be estimated by assigning charge states to the peaks.

2. Calculate Protein Molecular Weight:

   • The highest peak typically corresponds to the highest charge state. Assuming the highest peak (1413.58) corresponds to a charge state of +1: \[ MW = 1413.58 \text{ Da} \]

   • If we assume the peak at 1413.58 corresponds to a +2 charge state, then: \[ MW = 1413.58 \times 2 = 2827.16 \text{ Da} \]

   • Continue this for other peaks by assuming its charge states could be +1, +2, and so on.

3. Organizing More Peaks: We analyze other peaks to see patterns or ratios:

   • For example, if:

     • 1413.58 (assumed +1) is the highest charge state.
     • 1211.77 is possibly +2 state, leading to MW of: \[ MW = 1211.77 \times 2 = 2423.54 \text{ Da} \]

   • Continue calculating possible MW for each charge state.

4. Final Estimation: After calculations, it’s common to determine a preferential molecular weight from a consensus from several peaks.

Summary

From the calculation, if 1413.58 Da is indeed the highest charge peak, taking it as +1, gives a molecular weight around 1413 Da, and for higher charge states (+2 to +4) gives molecular weights above this.

However, recognition of the charge states suggests the most probable value is observed from the peak with the multiplicative charges. A good candidate for the protein molecular weight might be around 2,800 Da if considering various charge ratios.

Note

Identifying exact charge states depends on the nature of the protein and experimental conditions. These estimates represent a common approach but should be confirmed with additional data and experimental validation when possible.