Calculating the pI of a peptide - Ch 3

[@MorganPedus]

this video has taught me more than my lecturer who has a PhD in biochemistry at an Ivy League University. Thank you so much.

[@DrMonaUCD]

Note: there’s a mistake on the overall charge of the peptide in the last step: it should be -1 not +1. Everything else is right :)

[@englishlife5838]

👍🏻

[@abdoulaziz808]

Thank you, for clarifying I couldn’t wrap my head around that.

[@lancekotter927]

Thank you! 🙏 I can't believe how simply you explained this! I have been trying to figure out how to do this for like a week because my current pHd professor was super overcomplicating it, thank you thank you thank you!!!!

[@esther_bea4039]

This video just boosted my mark to above 80%. This work was never explained to us so thank you so much. Will definitely recommend your videos

[@snguyen7311]

Good method. Just got to remember as pH raises it exceeds pka of ionizable groups from lowest pka to higher pka in order.

[@fatcammal]

This is the best method I've seen so far!

[@tayam6508]

I was so lost after my lecture. This cleared it up a lot! Very simple method, thank you :)

[@yazan4mjad]

Wow, as a student who has a lack of resources to study from this actually helped a lot, thanks this is much appreciated ❤

[@valcheung5747]

I think there is a mistake toward the last NH3+ group at pka 9.7. I think the charge should be -1 because the net charge right after pka 6 and before pka 9.7 is already 0. hence when have another depronotation after pka 9.7 it is supposed to have -1 over all here.

[@davonlee7660]

This is a great video. Preparing for the MCAT while also taking Biochem. Truly helpful. Thank you.

[@wesleatherman5726]

I'm pretty sure the charge at at the lowest pH should be +2(arg.+1 and n-terminal of Glu +1) Where did the 3 positive charge come from?

[@ekaterinadadgar4854]

Why do we use COOH as the R group for Glu when in another example we used RH+ just as we used for His, Arg, and COO-? If we use RH+ for our R group instead of COOH, wouldn't that change our starting charge too?

[@monamonfared7287]

You don't use RH+ for the COOH group bc COOH is neutral; protonation of a group does not always mean the group will be positive.

[@nathaliabarros410]

Thank you for your explanation. I'm having some difficults and this video really helped me!

[@cbzzbc3482]

Very useful video with detailed explanation🥰👍

[@nadinenajah9198]

best method I've seen! thanks for the super clear explanation!

[@soumyamajumdar7929]

can you please find the pI for ala-arg-gly.

[@shehzanshareef2087]

Pka of carboxly group of glutamate is 2.19

[@musiclover981010]

thank you for the clear explanation!

[@2ts562]

I would like to ask, how will I know which R group can I protonate and when will it be positive or neutral? =)

[@DrMonaUCD]

Since you imagine that you are starting with the peptide at a low pH, everything will be protonated. Then the groups will deprotonate, starting with the lowest one. How you know they are neutral, positive, etc? You have to memorize the structures :) and then understand what the group looks like when it’s in the acid form vs the conjugate base form

[@2ts562]

@@DrMonaUCD thank you for your reply!

[@jasonetchingham9587]

Careful of the mistake after pka 9.7 Doesn’t mess with the end result but it should have gone to -1 not +1

[@mdsydurrahman8811]

Excellent explanation

[@Raejae00]

this was very helpful thank you!

[@keheibamdingthou1330]

What about Arginine ? Why Glutamine ,the Ionizable group that has to deprotanate after histidine? Because histidine and arginine carry the same RH+

[@monamonfared7287]

you are right that they both have RH+ when the R group is protonated, but you have to look at the pKas to know which deprotonates first as you raise pH; they have different pKa values

[@VICTORCAMILOLEDESMA]

From what book did you get this problem from?

[@mriganka9312]

Lehningeer

[@007ETA73]

This video was super helpful!

[@DrMonaUCD]

Echoe Malone thank you!

[@mahsabayati491]

You are great! Thank you

[@itsmn_9027]

hello um I don’t mean to be mean or something i just have a question? aren't we supposed to take the one before and after the 6 one? like it's 0 charge on ph 6 so we should take 4 and 9 right? i don't know i don't get it well pls respond i have an exam xD thanks in advance

[@itsmn_9027]

Oh no no sorry I mixed ph and pka’s my bad no need to bother

[@jennyborbe559]

The video is good but you're so slow lol