Dear Wondimagegne Assefa Molla,

It seems you are trying to do peak fitting on the Amide I band of silk fibroin.

To this end, you should first know where your peaks should be.

Depending on the origin of the silk you used, you can find many articles dealing with the issue. Usually, there are about five components in the Amide I region of fibroin.

Once you identified where your peaks should be, I suggest using Origin that has a quite user-friendly interface to find the actual peaks.

However, I would suggest making sure you have the entire peak (in the attached file you provided only the data in the 1600 - 1670 cm-1 range, when the Amide I can sometimes be a bit wider (at least on the silks I analyse).

Then, juste draw a simple baseline to "flatten" your peak (straight line from edge to edge) and launch the peak fittting !

I should add that sometimes, looking at the Amide III peak can also be of interest if you want to retrieve data regarding the structure of your film.

I hope this could help you.

Regards,

Pauline Uring

Dear Wondimagegne Assefa Molla,

You don't need to set all those values for a correct peak fitting. I suggest you only set the relevant peak positions (and force Origin to keep with the selected positions).

I also advise you to pick Voigt curves (a mix of Lorentz and Gauss).

I suggest you to use this tool :

https://www.originlab.com/doc/Origin-Help/Fit-MultiPeakFit-Tool

And also, sometimes you don't want Origin to do everything by himself - so do the step by step fitting by pressing the button next to the "chi ²" button here :

https://www.originlab.com/doc/Origin-Help/NLFit-Dialog

This way, you can always "correct" Origin if it's starting to do weird things like putting negative peaks.

Regarding the file you attached, notice the tiny peak around 1699cm-1 : this one is important as well.

Please see in the literature as to where the relevant peaks should appear (and the Amide III would be interesting for you as well).

Best,

Pauline Uring

Thank you so much for your unlimited help!!

Dear Pauline Uring, I have one more question about calculating beta sheet, helix, turn and random coil. In one book, I saw example of calculating these secondary structures. For case of beta sheet, it seems wrong for me. Maybe, I don't know. I attached here with my answer in blue. Can you justify it please?You also suggested me curve fitting, but here curve fitting is after deconvolution. Thank you!

Wondimagegne A Mo Deconvolution of a composite peak into its individual peaks plays an important role in the interpretation of many types of graphs including XRD, XPS, FTIR, and PL etc. In this video, I have discussed how to deconvolute simple combined peaks, composite peaks and how to correct missing data in a given peak with the help of deconvolution. In the case you want to further ask about it, please do comment on the specific video, I'll respond to it shortly. I have provided the practice filee (OriginLab) here. Thanks

https://youtu.be/WX_X3XlbKRA