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[Ivan Neretin in the comments] It is neither. See, the whole thing is 3D. Take a paper sheet and draw an all-trans peptide chain along a straight line. Now roll up the paper into a cylinder and bend all residues outwards. That is so true. Here is an animation to illustrate: The peptide planes are still planar, and wrap around an imaginary cylinder. ...


2

Direct molybdenum method detects inorganic phosphorus/phosphates(1). To determine total phosphorus, a sample gets first mineralised, forming phosphates, e.g. at high temperature by peroxodisulphate oxidation(2). (1) I have used it interchangeably depending on if phosphate content is expressed as phosphorus or phosphate. It is advantageous to express ...


3

Biodegradation of polymers generally requires three conditions: There must be a way to break the high MW polymer molecules down into smaller MW pieces. With condensation polymers like polyesters and polyamides, the logical break points are the ester or amide bonds, which are broken by hydrolysis. Breaking a polyolefin such as polyethylene is much harder and ...


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For a reaction to happen, it is sufficient if 1 in a 1000 thiamine structures are deprotonated. For a species with a $\mathrm{p}K_\mathrm{a}$ of 18 to be 50% deprotonated, you would need an aqueous solution with a pH of 18, which is not possible as far as I know. So even if thiamine is present in aqueous solution and not (as mentioned in Rafael L's answer) ...


2

Instead of thinking about the instrumental (spectrophotometer) problems, re-think your experiment. You are testing the instrument at its typical performance limit. The absorbance of the method is too low! Let us convert the absorbance 0.0010 to percent transmittance. It is 99.77% What does that mean physically? You are "requesting" the instrument ...


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Diluting a detergent solution at the CMC will result in a transition from a micellized into a disaggregated state. The definition of the CMC is that it is the concentration of onset of micellization. Below this concentration micelles do not exist. For the diluted solution, surfactant in micelles will have a higher free energy than free detergent. In general, ...


4

The protein lysozyme (160 amino acids) has been synthesized using a flow reactor according to https://www.chemistryworld.com/news/protein-synthesis-revolution-on-way-as-large-peptides-made-in-hours-not-days/4011891.article . The same article suggest 50 amino acids as a cut-off where the traditional solid state synthesis would be infeasible.


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How can one quickly identify suspicious water molecules that might have been modelled wrong - or what one should be looking for if one suspects a particular water molecules to be something else. You can check how many ligands the water has, and what the distances are. Most water molecules can safely be ignored, except for ones in an active site or so. When ...


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Assignment refers to a statement that a particular amino acid residue (1) has a given backbone conformation described by dihedral angles falling within certain limits (2) based on the local conformation of a series that includes adjacent amino acids, the residue can be said to be part of a secondary structure such as one of various types of helix, sheet or ...


3

There is a fallacy in your experiment. Yes, absorbance is indeed additive tha low concentrations provided the reagents do not react. This sum property allows simultaneous determination or two or more components in a solution using the additive property of Beer's law. Note: When you zero the photometer you are not taking absorbance into account but a lot of ...


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Is the following statement true? Absorbance of a mix of two concentrations is the sum of the absorbances of the individual concentrations. My answer is need more information to give a correct answer. The statement is not clear about few things: It is not clear about the mixture of two concentrations are of the solutions of same reagents. If they are the ...


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