Questions tagged [structural-biology]

The study of the molecular structure of biological macromolecules and how that structure relates to their function.

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13 votes
4 answers
3k views

What are the benefits of elucidating the three-dimensional structure of a protein?

I have spent months as a student working on trying to form a tricky protein crystal. But I have never actually had explained to me why the structure will be useful. Once elucidated, what can we ...
1 vote
0 answers
56 views

What protein(s) bind together the calcium carbonate tiles in abalone shell to give it strength?

The articles that I've been able to find on the structure of abalone shells mention that they consist of calcium carbonate plates connected by proteins, but don't name the proteins. These proteins are ...
0 votes
0 answers
35 views

Determine directionality of backbone from electron density map

I am given a polypeptide with three electron density maps at different resolutions; 1.85, 2.5 and 3.5Å. And from this I am to determine at which resolution you could be certain about the ...
-1 votes
1 answer
39 views

Where is the location of cutin or cuticle in the plant leaf [closed]

Cutin's main role is to prevent the the plant leaf from water loss, cutin is thick in shape , but I need to know where is the location of it ,for example is it in the lower epidermis or in the upper ...
1 vote
0 answers
36 views

What is the structure of PduK in the Pdu BMC?

My lab is creating 1,2-propanediol utilization bacterial microcompartments (Pdu BMCs) with an operon containing genes for PduA, PduB, PduJ, PduK, PduN, PduU, and PduT. According to Mayer et al., all ...
7 votes
1 answer
143 views

How does the Endoplasmic Reticulum scale with Cell Volume in Epithelial Cells?

I am working on a mathematical model of a biological tissue (drosophila pupal notum; an epithelial tissue) where the tissue is built up from cells all described by the same cellular-model. The tissue ...
3 votes
0 answers
229 views

Automating figure-making with PyMOL [closed]

What I want to do I have a list of almost 200 PDB entries that I need to visually inspect. Luckily, the thumbnail image displayed on the PDB website (examples with RCSB or PDBe for a well-known ...
3 votes
1 answer
52 views

Using BLAST for molecular replacement in structural biology

This is my first time trying to do molecular replacement to solve a protein structure. I am using the NCBI blastp program to find suitable search models. When choosing a search model, I understand ...
-5 votes
2 answers
234 views

Why does DNA synthesis require nucleoside triphosphates? [closed]

Writing the DNA sequence is done with nuclosides that have three phosphates attached to them, and two of these phosphate are thrown away back into "phosphate pool" of cell. What are main ...
0 votes
0 answers
30 views

What is the structure of heterochromatin?

A short article about euchromatin and heterochromatin mentions that the structure of heterochromatin usually depicted in images "has never been visualized in vivo, and its existence is ...
0 votes
0 answers
65 views

Generating Cartesian coordinates of each atom in protein chain from the internal coordinates using python or some software

I am trying to compute Cartesian coordinates of backbone atoms and side-chain atoms (C beta alone) for a given set of internal coordinates (bond lengths, bond angles and dihedral angles) I have ...
-2 votes
1 answer
70 views

Do SILK fibres let light pass through it?

The reason given by Wikipedia for silk fibres being lustrous is that: Silk fibres have triangular prism-like structure, which allows them to refract the incoming light at different angles. By my ...
0 votes
1 answer
215 views

What is the difference between a myofibril and a myoblast? (In skeletal muscle)

I read that a muscle fibre (myofiber) is formed when myoblasts fuse. https://teaching.ncl.ac.uk/bms/wiki/index.php/Skeletal_muscle#:~:text=The%20multinucleate%20feature%20is%20established%20in%...
5 votes
1 answer
161 views

Tryptophan side-chain structure, how should it be orientated?

I would like some clarification on whether it matters where the NH and double bond are placed in these two structures of tryptophan (W) that I drew. I marked the right side as correct and the left ...
1 vote
1 answer
143 views

What are the uses of Helical Wheel Projections in Structural Biology?

I have seen helical wheel projections used to illustrate amphipathic helices in proteins. Are there any other uses for these models?
11 votes
1 answer
2k views

Coronavirus capsid missing?

According to several sources, Coronavirus is a helical virus, i.e. it should have a helical capsid. Although most sources did not labelled or pointed any kind of capsid. It was mysterious to watch ...
0 votes
1 answer
2k views

What is meant by "complexity of carbon sources"?

My biology book states "life on earth depends upon carbon based molecules, most of these food sources are also carbon based. Depending upon the complexity of these carbon sources, different ...
7 votes
2 answers
28k views

Why is the DNA helix anti-parallel? [duplicate]

Why is it that DNA strands are running in anti-parallel fashion? Given the chemical base-pairing, they could have been parallel just as well.
1 vote
1 answer
26 views

Is mucus significantly affected by the presence of ions?

In mucus, there is besides water and the mucins (Proteins for mucus), there are Ions like $Ca^{2+},Na^{+}$, etc. I have read that These Ions can Control the mucus swelling, i.e. the volume that the ...
2 votes
2 answers
138 views

Which proteins are most sensitive to electric fields?

Many Proteins have ionic charges that can attract each other (e.g. Formation of salt bridges) or repel each other. On the other Hand, Proteins are mostly immersed in water that screens most of the ...
0 votes
0 answers
38 views

"Straight" or "linear" helix

If an alpha helix is discontinued for a short while and then continues in a different direction, I prefer to call in "kinked". If the helix is simply uniformly following one direction, I prefer to ...
17 votes
1 answer
61k views

How can Valonia ventricosa cells get so big?

Valonia ventricosa are single-celled algae that range between one and few centimetres. In rare cases, they can reach sizes exceeding 5cm. They range from grass-green to dark green, and some are even a ...
10 votes
4 answers
1k views

Can protein structure be determined by X-Ray Diffraction in a single image?

I'm reading about the use of x-ray crystallography to determine protein structure. According to my book, data is collected at 30-360 angles (dependent on the symmetry of the protein). An illustration ...
7 votes
1 answer
5k views

What is the fibre axis in the Watson and Crick paper?

I was reading Watson and Crick’s original article on DNA structure in Nature 171, 737–738 (1953). The accompanying diagram (shown below) has something called the “fibre axis” going through the DNA. ...
0 votes
0 answers
70 views

What is the difference among biochemistry, molecular biology, molecular genetics and structural biology?

I have never heard of straigthforward definitions of these fields in my college lectures, and the Internet searches were not very helpful. However, from what I have learned at different subjects, this ...
1 vote
1 answer
78 views

How do fatty acid and polyketide synthases handle the varying size of their substrates?

Polyketide synthesis involves six modules, each containing certain common constituent enzyme activities (KS, AT, KR) that are involved in extending the chain (see e.g. Dutta et al.(2014) ). The ...
5 votes
1 answer
86 views

How many residues can a reliable ab initio structural model contain?

A recent question on ab initio that I answered involved touching on the limitations of ab initio modelling. A review from 2009 put forward that typically only in the order of 100-110 residues could be ...
4 votes
2 answers
756 views

Which server to use for volume and accessible surface area calculation of proteins

I want to find the accessible surface area and the volume of a protein, giving PDB file as the input for the protein. I used two servers, 3vee and Vadar. For the PDB id, 1LTM, the websites are giving ...
3 votes
1 answer
99 views

Is there a reason for the lack of full RTK structures?

Bocharov et al. (2013) write that As there are no structures of full-length RTKs [receptor tyrosine kinases], we do not fully understand how different domains function together to mediate signal ...
-2 votes
1 answer
150 views

Why is the macromolecular composition of a human cell seemingly hard to find?

I am trying to find a 3D rendering or list of molecules by volume in a cell (originally I was searching for human, but I'll take any at this point!). I understand the open-endedness of the question: ...
8 votes
2 answers
522 views

Solution based measurement of Solvent-Accessible Surface Area of macromolecules

The Solvent-Accessible Surface Area (SASA) is a valuable metric for looking at protein folding and protein-protein interactions. However, this measurement is typically done by calculating the SASA ...
1 vote
2 answers
373 views

What are the structural factors affect enzyme's Km?

Is there any rules (should not be exact), to estimate the kinetic changes in an enzyme if I did any mutation on it? If I cannot estimate the new kinetic values, is it possible at least to clarify or ...
3 votes
1 answer
3k views

Why we utilize dextro glucose and levo amino acids?

Our body only digest dextro(Right handed) glucose and levo(Left handed) proteins and can't digest Levo glucose and dextro proteins. Why? Our body synthesis levo proteins. What is the reason?
26 votes
3 answers
3k views

Does any molecule other than DNA have a double-helical structure?

DNA is known to have a double-helical structure. Do any other molecules have this structure?
1 vote
0 answers
25 views

Database of predicted protein-ligand binding/docking score

Is there a database of computationally determined "binding scores" across protein-ligand pairs in the PDB? My phrase "binding score" is deliberately generic, since any such score would be fine. In ...
1 vote
0 answers
86 views

How does antibody structure relate to function? [closed]

I know that antibodies have 2 binding sites (as Y shape) so they can bind to 2 pathogens for agglutination. They have a hinge, heavy and light chains, constant and variable sections on these chains. ...
3 votes
3 answers
174 views

What are the applications of predicting the structure of proteins?

Protein molecules are very important as they are used for catalyzing almost all the chemical reactions in the cell, regulation of gene activity and provide cellular structure. However, in predicting ...
3 votes
0 answers
64 views

Why can polar molecules like water pass aquaporin better than unpolar like H2 or CO2

We learned in our lecutre, that aquaporin lets Water pass, but blocks Ions like H+ and unpolar molecules like CO2 and H2. The reasons for the Ion blocking are comprehensible, but I dont get, why less-...
3 votes
1 answer
301 views

Why add hydrogens in molecular dynamics simulations?

In my molecular dynamics lecture, our prof said, that we always have to add hydrogen atoms to titratable groups, before we start the force field simulations, and that it is especially important for ...
3 votes
1 answer
371 views

Parallel DNA double-helices with Watson–Crick base-pairing: Why do they not occur? [duplicate]

I know that parallel DNA helices exist and are governed by Hoogsten base pairing, but why can’t they be possible with Watson-Crick pairing? In the diagram below, if we were to flip one of the strands ...
5 votes
1 answer
185 views

Generate mesh surface from protein structure

What tools are most widely used for generating a mesh surface of a protein from an x-ray crystallographic structure (from the PDB)? Pros and cons would be appreciated. I'd prefer the output to be a ...
7 votes
1 answer
231 views

RMSD during conformational transition in proteins

When I was investigating the differences between protein structures obtained by X-ray crystallography and NMR spectroscopy, I found the paper [1] compairing structures of several proteins resolved ...
2 votes
3 answers
92 views

Why does sequence of amino acids presented on the Catalytic Site Atlas from a given protein differs from the sequence on the RSCB Protein Data Bank

I wanted to compare the amino acid sequence of enzymes for this project I'm working on and need to compare them at their catalytic site. For that, I went to the Catalitic Site Atlas to get the ...
2 votes
0 answers
51 views

What is the biggest structure in nature for structural coloration?

I'm interested in the actual sizes behind structural coloration: I find it fascinating and I think it may have a couple very nice applications. The problem is I couldn't find anything but vague ...
8 votes
2 answers
2k views

How hard it is to determine a 3d structure of a protein?

I seeing tens of thousands of PDB files on the internet. I really want to determine a 3D structure of my protein of interest. I've heard that 3D structure determination is a complex, expensive, and ...
6 votes
2 answers
211 views

Are there functional examples of parallel DNA double helices?

The anti-parallel structure of the DNA double helix is well studied, but I am curious if there are any examples of parallel DNA double helices. There are reports of synthetic such structures; see this ...
0 votes
1 answer
1k views

What does "local folding" means in secondary structure?

I'm new to biology field, so I'm learning all kinds of biochemistry knowledge for a bioinformatics project. I've found a few definitions of secondary structure online. For example, I found this brief ...
6 votes
2 answers
1k views

Twist in the DNA double-helix

DNA, has a deoxyribose sugar — phosphate backbone with the purine and pyrimidine bases, adenine, cytosine, thymine, and guanine connected to the deoxyribose sugar. (The base–sugar molecules are ...
1 vote
1 answer
97 views

At what point, when connected, do DNA strands become a helix?

When synthesizing DNA strands and beginning to "connect" them, how quickly does it become a helix? In this answer, canadianer says The helical structure is more stable than the "straight" form (...
11 votes
1 answer
5k views

In which direction does ATP synthase rotate?

I heard about the rotation of ATP synthase in a biochemistry course. The professor said it will rotate counterclockwise. Is that true? If so, what mechanism defines its direction?