69

Crystallin proteins are found in the eye lens (where their main job is probably to define the refractive index of the medium); they are commonly considered to be non-regenerated. So, your crystallins are as old as you are! Because of this absence of regeneration, the accumulate damage over time, including proteolysis, cross-linkings etc., which is one of ...


22

I like Mowgli's answer, because it is a non-obvious example. However I would also point out that there are many, many protein-based structural components in the body that we know do not regenerate due to associated pathologies; so presumably these structural proteins are as old as from when they first arose in developemnt. Take the stereocilia on hair cells ...


20

(my comment reiterating the answer seemed useful, so I've reproduced it here) There are "NMDA receptors" in our body. There is not NMDA naturally in our body*. "NMDA receptor" is just a name people gave to one of the receptors that normally binds glutamate. They could have called it something else, like the "slow glu receptor", or "Glutamate Receptor A", ...


9

A very interesting example are the cohesin molecules holding sister chromatids together in the oocytes (so only applicable to females, sorry!). Cohesion is established in utero, and these molecules are not recycled throughout life (AFAIK only shown directly for mice, not humans - https://www.ncbi.nlm.nih.gov/pubmed/20971813, https://www.ncbi.nlm.nih.gov/...


9

Chaperone proteins are still proteins and they can certainly misfold just like any other. If that happens, it will either be assisted by another chaperone and given time to fold successfully or it will be destroyed. If this is happening too often and the amount of chaperones drops too low or the number of unfolded or incorrectly folded proteins becomes ...


8

Your question is rooted in a misundertsanding of the hydrophobic effect. Hydrophillic and hydrophobic molecules do not repel but, rather, attract one another through van der Waals interactions. The tendency of hydrophobic molecules to aggregate in aqueous solution (ie the hydrophobic effect) is, instead of some repulsive force, actually driven entropically. ...


8

Dr. Bailey wrote a short piece that hints at the reasons behind why she expected what she expected: Telomeres are the ends of chromosomes that protect them from damage and from “fraying” – much like the end of a shoestring. Telomeres are critical for maintaining chromosome and genome stability. However, telomeres naturally shorten as our cells divide, and ...


7

This question is, in my opinion, based on an incorrect premise but nevertheless throws up a number of points about protein folding and protein structure that can be addressed, albeit briefly. The False Premise “it is a generally accepted idea that protein folding is completely determined by the sequence of amino acids” (My emphasis.) No… What is ...


7

I don't know precisely what you mean by "analyze", which could be anything from simply "view" or "measure distances", to evaluating an energy function on a crystal structure or molecular dynamics simulation, to prediction of binding sites de novo. The tools are different for each case, though some can do several things. For simply viewing, measuring ...


6

Short answer Some genes on the X chromosome escape X-inactivation. Two copies of these genes are needed for normal development. These genes are also present on the Y chromosome. Hence, healthy males and females both have two copies of these genes. In Turner's, the SHOX gene seems to be one of the culprits, which is needed for normal skeletal development. ...


6

It doesn't make sense to set volumes of decimals of microliters with a P200, since usually the accuracy of these pipettes is in the order of a few microliters. So even if you set your pipette at 190 uL, you may still dispense a volume ranging from 187 to 193 uL. For a P1000, due to higher volumes the inaccuracy is of course higher, usually +/- 10 uL or more. ...


6

The PubChem format description is not that easy to find: https://www.ncbi.nlm.nih.gov/IEB/ToolBox/CPP_DOC/asn_spec/pcsubstance.asn.html And the ASN file linked here: https://pubchemdocs.ncbi.nlm.nih.gov/data-specification I am correct in saying that the numbers in the 'element' array are corresponding to Atomic Numbers? Yes, 1 is hydrogen, 6 is carbon, ...


6

The premise of the questions suggests that mutations cannot take place in the mRNAs of higher eukaryotes. To answer your question I think it is important to consider two viewpoints: First, from a theoretical point of view, since DNA and RNA are as you pointed out composed of nucleic acids, they both can be mutated if enough energy is provided (UV light, ...


5

There's actually no need to speculate on the answer to this question since scientists have published their estimates and methodology, as is their way. The following paper is a good review: Fields C, Adams MD, White O, Venter JC. 1994. How many genes in the human genome? Nature Genetics 7:345-346. Below are some truncated excerpts from the paper but, if ...


5

I wouldn't really say RNA polymerase is "creating" the hydrogen bonds so much as it's thermodynamics that creates them. When we talk about an enzyme "creating" a bond, what we're generally referring to is an enzyme facilitating a reaction by lowering its activation energy so that it can proceed. However, in the hydrogen bonding between base pairs, there's ...


5

I found this paper, which goes very deep into the molecular details of the individual steps of this reaction and also discusses how this is coupled to nucleotide selectivity. The 'basic' details about the reaction (quoted from this section, which also has a nice figure): The polymerization reaction proceeds by a simple nucleophilic attack of the 3'OH ...


5

The textbook is asserting that translation could function without redundant codons, not that it does. In reality, all possible codons are used. See this answer on the interchangeability of codons.


5

It is standard IUPAC nomenclature to write bases that are not uniquely defined. For example, "N" means "any base", but "V" means "A, C or G, but not T". See the full list here


5

If you look at the Google ngram for the term ‘Molecular Biology’ you will see that it first appears just before 1960, and it is relevant that the Journal of Molecular Biology was founded in 1959. It is not biochemistry — indeed the name was meant to indicate its difference from biochemistry, and I heard second-hand (so I cannot vouch for its truth) that Hans ...


5

It sounds a bit like chem exam question to be honest... Or at least the answer does... namely that O2 being paramagnetic creates a "spin barrier" that prevents most organic compounds from reacting fast with atmospheric oxygen: The magnetic properties of O2 are not just a laboratory curiosity; they are absolutely crucial to the existence of life. Because ...


5

In humans, cysteine can be synthesized from methionine and tyrosine from phenylalanine (note that the reverse pathways do not occur). Because their synthesis requires essential amino acids and the biosynthetic capacity of the organism does not always meet its need, they have been labelled conditionally essential. Under normal circumstances, an adult human ...


5

The two techniques serve different purposes: IP: purifies a protein WB: visualizes or quantifies a protein Most often when I have done IPs (in the hazy past) I have turned around and run the protein out on a WB, so one will frequently combine both techniques. Sometimes a protein is very low abundance so you will not see it in a small volume of crude cell ...


5

You seem to be under the impression that there are a set number mutations per cell, which is not true. The number of mutations is roughly proportional to the number of bases — this is because mutations typically happen as a result of errors during DNA replication .1 Consequently, more DNA will not protect the coding portions of the genome from mutation. ...


4

The problem statement says all the proteins have the same molecular weight but does not say how many amino acids they have. It does say how many cysteine amino acids each has, but not how many other kinds they have. Cysteine forms disulfide bonds, holding bends in the protein structure. BiteSizeBio says: SDS is a detergent that is present in the SDS-...


4

The term ‘redundant’ is not ideal in this respect, as that implies a redundancy in reality rather than theory, as @canadianer points out. Redundancy and Degeneracy However I would mention that there is another term more usually applied to the fact that certain amino acids are encoded by more than one codon — degeneracy. There is a Wikipedia entry on ...


4

@AliceD's answer is excellent, but I thought it would be helpful to include an additional perspective. The issue here isn't that monosomy X shouldn't be a problem because the majority of one X chromosome is inactivated. It is that monosomy X isn't as big a problem as any other monosomy because the majority of one X chromosome is inactivated. Monosomies ...


4

This DSSP page makes it clear that: Helix-3 = 3-10 helix Helix-5 = π-helix The α-helix) is described in every biochemistry text book and widely on the web. It has 3.6 residues per helical turn and has 13 atoms in the ring formed by the hydrogen bond and so can also be called a 3.6-13 helix. The 3-10 helix is less common than the α-helix, but is ...


4

The answer to your re-phrased question "Do any chemical processes occurring within the physical volume of any entiy considered "living" depend in any way, shape, or form on oxygen's paramagnetic properties? is an emphatic 'yes', and this answer may be substantiated with a single word: haemoglobin. Pauling and Coryell discovered in 1936 that the ...


4

The heads and tails, in this paper, refer to the orientation of sgRNA binding sites. If there are two tandem sites in the same orientation then they are referred to as head-to-tail (end of the first site followed by the beginning of the second site). It is also apparent from the excerpt that you have included in your question. Head-to-head and tail-to-tail ...


4

While you’re correct that NK cells are often activated (in part) by the absence of MHC-I, they require other signaling events to become fully activated: The Molecular Mechanism of Natural Killer Cells Function and Its Importance in Cancer Immunotherapy. Paul & Lal. Frontiers in Immunology. 2017. Activating Receptors on NK Cells Lack of MHC ...


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