Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Netiquette · Download · News · Gallery · Homepage · DSSR Manual · G-quadruplexes · DSSR-Jmol · DSSR-PyMOL · DSSR Licensing · Video Overview· RNA Covers

Messages - xiangjun

Pages: 1 [2] 3 4 ... 64
26
RNA structures (DSSR) / Re: Creation of customized structures using DSSR
« on: October 12, 2023, 11:11:25 am »
Also "RNAfitme: a webserver for modeling nucleobase and nucleoside residue conformation in fixed-backbone RNA structures" (https://bmcbioinformatics.biomedcentral.com/articles/10.1186/s12859-018-2317-9):

Quote
Here, we present RNAfitme, a versatile webserver tool for remodeling of nucleobase- and nucleoside residue conformations in the fixed-backbone RNA 3D structures. Our approach makes use of dedicated libraries that define RNA conformational space. They have been built upon torsional angle characteristics of PDB-deposited RNA structures. RNAfitme can be applied to reconstruct full-atom model of RNA from its backbone; remodel user-selected nucleobase/nucleoside residues in a given RNA structure; predict RNA 3D structure based on the sequence and the template of a homologous molecule of the same size; refine RNA 3D model by reducing steric clashes indicated during structure quality assessment. RNAfitme is a publicly available tool with an intuitive interface. It is freely accessible at http://rnafitme.cs.put.poznan.pl/

27
RNA structures (DSSR) / Re: Creation of customized structures using DSSR
« on: October 12, 2023, 11:06:59 am »
Have a look at "The proto-Nucleic Acid Builder: a software tool for constructing nucleic acid analogs" (https://academic.oup.com/nar/article/49/1/79/6029180):

Quote
"To aid the development of novel XNA polymers and the search for possible pre-RNA candidates, this article presents the proto-Nucleic Acid Builder (https://github.com/GT-NucleicAcids/pnab), an open-source program for modeling nucleic acid analogs with alternative backbones and nucleobases. The torsion-driven conformation search procedure implemented here predicts structures with good accuracy compared to experimental structures, and correctly demonstrates the correlation between the helical structure and the backbone conformation in DNA and RNA."

Please report back how it goes.

Best regards,

Xiang-Jun

28
RNA structures (DSSR) / Re: Creation of customized structures using DSSR
« on: October 12, 2023, 08:50:01 am »
Thanks for your follow-up.

Quote
By the 9 torsional angles, I meant the torsional and pseudotorsional angles - alpha, beta, gamma, delta, chi, epsilon, zeta, eta, theta - calculated by 3DNA's `analyze` program.

Among the 9 torsion angles, only the first 7 are independent. The last two, eta and theta, could in principle be deduced from (alpha, beta, gamma, delta, epsilon, zeta). I vaguely remember reading about software tools of building nucleic acid structures using backbone torsion angles, including only eta and theta. I just do not know how useable they are from a general user's perspective.

Quote
DSSR would indeed benefit from more modeling features! I'll be following the release notes to see if this particular modeling feature is ever introduced to DSSR.

If you have info in modeling nucleic acids, please share them along this thread. I appreciate your kind words on DSSR.

Best regards,

Xiang-Jun


29
RNA structures (DSSR) / Re: Creation of customized structures using DSSR
« on: October 12, 2023, 08:18:44 am »
Hi,

Thanks for your using 3DNA, and your inquiries about DSSR Pro.

Quote
I apologize if this question is irrelevant for the forum, I wanted to confirm if DSSR Pro could satisfy our requirements before buying the license since the Pro version of the manual is not available.

It is directly relevant to the Forum. You are very welcome to post this question, and any more you may have.


Quote
We have an RNA sequence, and the 9 torsional angles (calculated by 3DNA v2.4) for each residue. Would it be possible to reconstruct the full-atom 3D structure of the RNA using DSSR Pro's rebuild program from just these two pieces of information - the sequence and the 9 torsional angles?

No, at least for now, even though it is not clear to me what exactly are the 9 torsional angles you refer to. DSSR employs 6 rigid-body parameters to quantity the relative spatial geometry between two bases (or base pairs) and uses them to build 3D models with approximate backbones. I have long been interested in adding more modeling features to DSSR ...

Best regards,

Xiang-Jun


30
FAQs / Re: Where to download x3DNA
« on: September 22, 2023, 11:53:22 am »
Done.

31
RNA structures (DSSR) / Re: Classification of helix versus loops
« on: July 06, 2023, 08:20:52 pm »
Hi Julia,

Please read the 2015 NAR paper "DSSR, an integrated software tool for dissecting the spatial structure of RNA" and the thread "Reproducing results published in the DSSR-NAR paper".

When asking questions, please be specific so other can understand exactly what you mean. I am glad the know that DSSR is being used by undergraduate students. Your instructor may provide you better help on the topics.

Also read the thread "No more grant funding for 3DNA/DSSR".

Best regards,

Xiang-Jun


32
The modified nucleotide J0C in 7E9E and 7E9I does not follow the naming convention of canonical bases. 3DNA can not handle it and thus the error message you reported.

DSSR can run successfully on these two PDB entries.

33
FAQs / Re: Where to download x3DNA
« on: December 25, 2022, 11:37:20 am »
See the FAQ "How to make the best use of the Forum".

Your account has been granted download access.

34
See the paper "DSSR: an integrated software tool for dissecting the spatial structure of RNA" (https://doi.org/10.1093/nar/gkv716).

Quote
Identification of nucleotides

        Note that pseudouridine (PSU) is shortened to ‘P’, due to its special C1′–C5 glycosidic link- age (Figure 2).

The M–N versus M+N relative base orientations

35
Hi Andrea,

DSSR Pro can do what you want very easily, especially in combination with the --json option. See No more grant funding for 3DNA/DSSR.

Base atoms have always been necessary for the identification of nucleotides in order to calculate base-pair and backbone parameters in 3DNA v2.x, including the command you mentioned: analyze -t=torsions.out. However, since 3DNA v2.x is open source for academic uses, you can modify it to meet your needs.

Best regards,

Xiang-Jun

36
Site announcements / Re: Clarification on DSSR licensing
« on: August 11, 2022, 09:24:51 am »
Hi Dr. Baulin,

Quote
is it safe to freely use the old DSSR version for academic use according to the old license?

Yes. Keep in mind that such outdated versions are no longer supported or maintained.

Best regards,

Xiang-Jun

37
Hi Amir,

Thanks for your support of the DSSR project by purchasing an academic license. As noted in the announcement post "No more grant funding for 3DNA/DSSR", I am committed (now in my 'spare time') to making DSSR a brand that stands for quality and value. I strive to provide paying users the best support they can expect from a software product. The objective is to ensure that the time and effort saved by using DSSR well outweighs the licensing charge, particularly the $1,000 one-time fee for academic users. As an example, did you realize how much time and work you save by getting DSSR up and running vs other software tools you are familiar with?

Now, let's get back to your precise question. I understand what you mean, but the information you supplied is insufficient to demonstrate the problem. Could you provide a minimum example that can reproduce exactly what you want to achieve?

DSSR Pro users, particularly those in the (pharmaceutical) industry, are oftentimes concerned about the data they are willing to share with the public. Thus I've been assisting them via email, phone, WeChat, or Zoom: whatever is convenient and effective. We can keep the topic going on the Forum, or you may wish to go private.

Best regards,

Xiang-Jun

38
The DSSR-PyMOL schematics have been featured in all 12 cover images (January to December) of the RNA Journal in 2021. Moreover, the January 2022 issue of RNA continues to highlight DSSR-enabled schematics (see the note below). In the current Covid-19 pandemic, this cover seems to be a fit for the upcoming Christmas holiday season.

Quote
Ebola virus matrix protein octameric ring (PDB id: 7K5L; Landeras-Bueno S, Wasserman H, Oliveira G, VanAernum ZL, Busch F, Salie ZL, Wysocki VH, Andersen K, Saphire EO. 2021. Cellular mRNA triggers structural transformation of Ebola virus matrix protein VP40 to its essential regulatory form. Cell Rep 35: 108986). The Ebola virus matrix protein (VP40) forms distinct structures linked to distinct functions in the virus life cycle. VP40 forms an octameric ring-shaped (D4 symmetry) assembly upon binding of RNA and is associated with transcriptional control. RNA backbone is displayed as a red ribbon; block bases use NDB colors: A—red, G—green, U—cyan; protein is displayed as a gold ribbon. Cover image provided by the Nucleic Acid Database (ndbserver.rutgers.edu). Image generated using DSSR and PyMOL (Lu XJ. 2020. _Nucleic Acids Res_ *48*: e74).

Thanks to Dr. Cathy Lawson at the NDB for generating these cover images using DSSR and PyMOL for the RNA Journal. I'm gratified that the 2020 NAR paper is explicitly acknowledged: it's the first time I've published as a single author in my scientific career.


Did you know that you can easily generate similar DSSR-PyMOL schematics via the http://skmatic.x3dna.org/ website? It is "simple and effective", "good for teaching", and has been highly recommended by Dr. Quentin Vicens (CU Denver) in FacultyOpinions.com.



The 12 PDB structures illustrated in the 2021 covers are:
  • January 2021 "iMango-III fluorescent aptamer (PDB id: 6PQ7; Trachman III RJ, Stagno JR, Conrad C, Jones CP, Fischer P, Meents A, Wang YX, Ferre-D'Amare AR. 2019. Co-crystal structure of the iMango-III fluorescent RNA aptamer using an X-ray free-electron laser. Acta Cryst F 75: 547). Upon binding TO1-biotin, the iMango-III aptamer achieves the largest fluorescence enhancement reported for turn-on aptamers (over 5000-fold)."
  • February 2021 "Human adenosine deaminase (E488Q mutant) acting on dsRNA (PDB id: 6VFF; Thuy-Boun AS, Thomas JM, Grajo HL, Palumbo CM, Park S, Nguyen LT, Fisher AJ, Beal PA. 2020. Asymmetric dimerization of adenosine deaminase acting on RNA facilitates substrate recognition. Nucleic Acids Res. https://doi.org/10.1093/nar/gkaa532). Adenosine deaminase enzymes convert adenosine to inosine in duplex RNA, a modification that strongly affects RNA structure and function in multiple ways."
  • March 2021 "Hepatitis A virus IRES domain V in complex with Fab (PDB id: 6MWN; Koirala D, Shao Y, Koldobskaya Y, Fuller JR, Watkins AM, Shelke SA, Pilipenko EV, Das R, Rice PA, Piccirilli JA. 2019. A conserved RNA structural motif for organizing topology within picornaviral internal ribosome entry sites. Nat Commun 10: 3629)."
  • April 2021 "Mouse endonuclease V in complex with 23mer RNA (PDB id: 6OZO; Wu J, Samara NL, Kuraoka I, Yang W. 2019. Evolution of inosine-specific endonuclease V from bacterial DNase to eukaryotic RNase. Mol Cell 76: 44). Endonuclease V cleaves the second phosphodiester bond 3′ to a deaminated adenosine (inosine). Although highly conserved, EndoV change substrate preference from DNA in bacteria to RNA in eukaryotes."
  • May 2021 "Manganese riboswitch from Xanthmonas oryzae (PDB id: 6N2V; Suddala KC, Price IR, Dandpat SS, Janeček M, Kührová P, Šponer J, Banáš P, Ke A, Walter NG. 2019. Local-to-global signal transduction at the core of a Mn2+ sensing riboswitch. Nat Commun 10: 4304). Bacterial manganese riboswitches control the expression of Mn2+ homeostasis genes. Using FRET, it was shown that an extended 4-way-junction samples transient docked states in the presence of Mg2+ but can only dock stably upon addition of submillimolar Mn2+."
  • June 2021 "Sulfolobus islandicus Csx1 RNase in complex with cyclic RNA activator (PDB id: 6R9R; Molina R, Stella S, Feng M, Sofos N, Jauniskis V, Pozdnyakova I, Lopez-Mendez B, She Q, Montoya G. 2019. Structure of Csx1-cOA4 complex reveals the basis of RNA decay in Type III-B CRISPR-Cas. Nat Commun 10: 4302). CRISPR-Cas multisubunit complexes cleave ssRNA and ssDNA, promoting the generation of cyclic oligoadenylate (cOA), which activates associated CRISPR-Cas RNases. The Csx1 RNase dimer is shown with cyclic (A4) RNA bound."
  • July 2021 "M. tuberculosis ileS T-box riboswitch in complex with tRNA (PDB id: 6UFG; Battaglia RA, Grigg JC, Ke A. 2019. Structural basis for tRNA decoding and aminoacylation sensing by T-box riboregulators. Nat Struct Mol Biol 26: 1106). T-box riboregulators are a class of cis-regulatory RNAs that govern the bacterial response to amino acid starvation by binding, decoding, and reading the aminoacylation status of specific transfer RNAs."
  • August 2021 "CAG repeats recognized by cyclic mismatch binding ligand (PDB id: 6QIV; Mukherjee S, Blaszczyk L, Rypniewski W, Falschlunger C, Micura R, Murata A, Dohno C, Nakatan K, Kiliszek A. 2019. Structural insights into synthetic ligands targeting A–A pairs in disease-related CAG RNA repeats. Nucleic Acids Res 47:10906). A large number of hereditary neurodegenerative human diseases are associated with abnormal expansion of repeated sequences. RNA containing CAG repeats can be recognized by synthetic cyclic mismatch-binding ligands such as the structure shown."
  • September 2021 "Corn aptamer complex with fluorophore Thioflavin T (PDB id: 6E81; Sjekloca L, Ferre-D'Amare AR. 2019. Binding between G quadruplexes at the homodimer interface of the Corn RNA aptamer strongly activates Thioflavin T fluorescence. Cell Chem Biol 26: 1159). The fluorescent compound Thioflavin T, widely used for the detection of amyloids, is bound at the dimer interface of the homodimeric G-quadruplex-containing RNA Corn aptamer."
  • October 2021 "Cas9 nuclease-sgRNA complex with anti-CRISPR protein inhibitor (PDB id: 6JE9; Sun W, Yang J, Cheng Z, Amrani N, Liu C, Wang K, Ibraheim R, Edraki A, Huang X, Wang M, et al. 2019. Structures of Neisseria meningitidis Cas9 complexes in catalytically poised and anti-CRISPR-inhibited states. Mol Cell 76: 938­–952.e5). Nme1Cas9, a compact nuclease for in vivo genome editing. AcrIIC3 is an anti-CRISPR protein inhibitor."
  • November 2021 "Two-quartet RNA parallel G-quadruplex complexed with porphyrin (PDB id: 6JJI; Zhang Y, Omari KE, Duman R, Liu S, Haider S, Wagner A, Parkinson GN, Wei D. 2020. Native de novo structural determinations of non-canonical nucleic acid motifs by X-ray crystallography at long wavelengths. Nucleic Acids Res 48: 9886–9898)."
  • December 2021 "Structure of S. pombe Lsm1–7 with RNA, polyuridine with 3' guanosine (PDB id: 6PPV; Montemayor EJ, Virta JM, Hayes SM, Nomura Y, Brow DA, Butcher SE. 2020. Molecular basis for the distinct cellular functions of the Lsm1–7 and Lsm2–8 complexes. RNA 26: 1400–1413). Eukaryotes possess eight highly conserved Lsm (like Sm) proteins that assemble into circular, heteroheptameric complexes, bind RNA, and direct a diverse range of biological processes. Among the many essential functions of Lsm proteins, the cytoplasmic Lsm1–7 complex initiates mRNA decay, while the nuclear Lsm2–8 complex acts as a chaperone for U6 spliceosomal RNA."

39
Site announcements / BioExcel webinar on DSSR
« on: November 23, 2021, 11:38:53 am »
On December 9, 2021, at 15:00 CET, I will present a BioExcel webinar titled "X3DNA-DSSR, a resource for structural bioinformatics of nucleic acids."

For the record, the screenshot of the announcement is shown below:


40
Site announcements / No more grant funding for 3DNA/DSSR
« on: October 30, 2021, 09:58:15 pm »
Due to a lack of governmental funding support, we are no longer able to provide DSSR free of charge to the community. Academic users may submit a license request for DSSR Basic or DSSR Pro by clicking "Express Licensing". Commercial users may inquire about pricing and licensing terms by emailing techtransfer@columbia.edu, copying xiangjun@x3dna.org.

DSSR Pro excels in structural bioinformatics of RNA, DNA, and their protein complexes. The software has completely superseded 3DNA, and is being continuously improved. Revenue from licensing supports the development and availability of DSSR.

I am committed to making DSSR a brand that stands for quality and value. By virtue of its unmatched functionality, usability, and support, DSSR saves users a substantial amount of time and effort when compared to other options.

I designed, implemented, documented, and have continuously improved and supported DSSR. As a result, DSSR users may expect a rapid and concrete answer to their questions. My track record throughout the years has unambiguously demonstrated my dedication to DSSR. I strive to ensure that paying users' trust in DSSR is well-founded by providing them with the best services possible.

As a general rule, the CTV does not provide an evaluation license of DSSR. Potential users should watch the DSSR overview video (20m), browse the Forum, and read DSSR-related papers. If they still have questions or want to see a live demo, I would be pleased to accommodate them. Although more DSSR licenses are definitely beneficial, I do not have the time or desire to directly promote the product, including sending bulk emails to registered users of the Forum. As the developer, I can only strive to make DSSR the best it can be and let the rest sort itself out. I am a strong believer of the old Chinese saying: "酒香不怕巷子深" (Good wine needs no bush).


3DNA is obsolete and no longer maintained or supported. Thanks to the revenue from DSSR licenses, however, the following web-based resources remain accessible to the general public:
Additionally, the 3DNA Forum will be maintained so that people can assist one another and archived content would remain accessible. I may chime in occasionally, but I will not be able to continue serving the community for free as I did over the past decade.


41
As mentioned in my previous response, DSSR Pro has options to handle such cases, among other features.

DSSR Pro's default output reports 146 nucleotides, along with a diagnostic note for the two deformed bases. Such deformed bases can participate in a variety of loops but not in pairing interactions.

Quote
Processing file '6nd42.pdb'
  2.G.248 0.808 -- distorted, without fitted base frame
  2.G.323 0.319 -- distorted, without fitted base frame
    total number of nucleotides: 146

DSSR Pro also has an option that treats those distorted bases as normal for base-pairing interactions.

42
DSSR is behaving as designed. Please see the section "Identification of nucleotides" of  the 2015 DSSR paper:

Quote
A nucleotide is identified if a residue contains at least three base ring atoms and the root-mean-square deviation (rmsd) of the fit falls below a user-definable cutoff. Since base rings are rigid, the rmsd is normally <0.1 Å. To account for experimental error and special non-planar cases, such as 5,6-dihydrouridine (H2U) in yeast tRNAPhe (Figure 2), the default rmsd cutoff is set to 0.28 Å.

The default DSSR cutoff values are based on extensive tests in real-world applications. Any unidentified nucleotide is almost always due to heavy distortions in its base geometry that is 'beyond recognition'. For example, G248 in your attached 6nd42.pdb file has the PyMOL rendered image as attached. Note the N1-C2 distance is 2.2 Å, far larger than ~1.5 Å (the normal covalent C-N bond length).

DSSR Pro has provisions to handle extreme cases like yours.

43
RNA structures (DSSR) / Re: DSSR output
« on: October 07, 2021, 09:47:56 am »
Which version of DSSR are you using?

44
Hi Ying,

Given the information you provided, I can only conclude that there must be some oddity in your structure at the places where 3DNA is unable to detect the base pairs. I cannot provide any further advice before seeing the structure (or the relevant section of it).

Xiang-Jun

45
Please provide a concrete example.

46
RNA structures (DSSR) / Re: How to get DSSR up and running?
« on: September 15, 2021, 11:56:26 am »
Hi Ying,

Quote
I am sorry that I forgot to update you on the progress.
Yes. I have downloaded the DSSR basic.


It is beneficial to update each topic you began so that other readers have a complete knowledge of what has occurred.

Quote
After I downloaded the DSSR software, I decompressed it and there are two files (DSSR manual and x3dna-dssr.exec) without further installation. I tried both computers, attached please find two images after I opened the .exec file. It seems that the software did not work. Is there anything wrong?

DSSR was designed with simplicity in mind. There are just two files distributed: a self-contained binary executable [x3dna-dssr (macOS and Linux) or x3dna-dssr.exe for Windows] as well as the associated PDF user manual. Because DSSR is a command-line software, it must be executed from a terminal window.

From the screenshot you attached, you are on macOS and DSSR is running as expected. Presumably, you've double-click x3dna-dssr to run it, as shown below:
x3dna-dssr ; exit;

So DSSR simply prints some help message and then exit. You must have a basic understanding of how to execute command line programs on macOS to run DSSR.

missing required option: must specify -i=PDBFile/mmCIF

type: 'x3dna-dssr -h (or --help)' for further help
      'x3dna-dssr --citation' for preferred citation(s)

Time used: 00:00:00:00

[Process completed]



Quote
Next, let me explain why I want to download the software DSSR. I used the 3DNA web sever before, but there are several base pairs missing, which may result in the incorrect calculation for the width of the major and minor groove of our RNA structure. I searched the forum and found that it may be due to the default setting for the website.  So I want to download the software and reset the parameters to see whether it can recognize the base pairs and measure the width again.

3DNA v2.4 is open source and is available to academic users after registering on the 3DNA Forum. If you have any particular queries about 3DNA v2.x, please submit them in the "General discussions (Q&As)" or "w3DNA — web interface to 3DNA" section.

Quote
In addition, I tried the DSSR web server, it failed because there was an error: Data too long for column 'jobid' at row 1. I also tried to analyze one published RNA structure (4j50)

Web DSSR (http://wdssr.x3dna.org) is an unpublished work, therefore bugs are to be expected. However, it generally behaves as designed. I've just tried PDB entry 4j50 without a problem.

Please remember to include specifics so that others can REPRODUCE reported problems.

Quote
I found that there is no information about the groove width of the helix from DSSR web. So I wonder if the information will be provided by DSSR basic version?

DSSR Basic does not include some features of 3DNA v2.4; DSSR Pro does. As noted on the post "Clarification on DSSR licensing",  "DSSR Basic includes features described in the three DSSR papers (2015 DSSR, 2017 DSSR-Jmol, and 2020 DSSR-PyMOL, all published in NAR) so that reported results can be reproduced."



Users are encouraged to post any 3DNA/DSSR-related queries on the Forum. Please keep in mind to be detailed and to offer follow-up on each thread.

Best regards,

Xiang-Jun

47
RNA structures (DSSR) / Re: Where to download the DSSR basic version
« on: September 13, 2021, 10:16:10 am »
Hi Ying,

Thanks for your follow up. DSSR-related issues are always welcome.

I can see your registration for a DSSR Basic license, as given by the CTV, as of this writing. It is now Monday morning (New York time), which may explain the delay you are experiencing. DSSR licenses are often processed quickly by the CTV support staff. Please keep us informed on your progress. If you haven't heard back from CTV by the end of the day, I'll contact them about your situation.

Best regards,

Xiang-Jun

48
RNA structures (DSSR) / Re: Where to download the DSSR basic version
« on: September 10, 2021, 11:18:59 pm »
Hi Ying,

DSSR may only be downloaded from the Columbia Technology Venture (CTV) website. I've included a link to the CTV website in several places on this 3DNA Forum. I'm surprised that users like you are still having trouble locating where to get DSSR.

To clarify, I changed the header link "DSSR License" to "DSSR Download/Licensing". The DSSR download link is also included in my signature at the bottom of each of my posts. See also the post "Clarification on DSSR licensing".

Registration on the 3DNA Forum is required in order to obtain the classic 3DNA v2.4 (and SCHNAaP/SCHNArP), and ask 3DNA/DSSR-related questions.

Please let me know if there is anything else I can do to make this message crystal clear.

Best regards,

Xiang-Jun

49
As a followup, DSSR Pro now has the option to derive only pairs across chains.

50
DSSR Basic does not have the base mutations feature at all. Also note that DSSR Basic is provided AS IS without any warranty of support.

That said, DSSR Basic does include features described in the three DSSR papers (2015 DSSR, 2017 DSSR-Jmol, and 2020 DSSR-PyMOL, all published in NAR) so that reported results can be reproduced. The DSSR Basic manual should function as expected. Anything to the contrary will be considered a bug and will be fixed as soon as possible.

DSSR Pro includes new advanced features, plus all functionality of 3DNA v2.4, as well as full support. Please watch the DSSR Overview Video.

Instead of DSSR/3DNA v2.4, you may want to try other software tools such as RNAView, FR3D, MC-Annotate, or Curves+ etc. Please let us know what you find.

Best regards,

Xiang-Jun

Pages: 1 [2] 3 4 ... 64

Funded by the NIH R24GM153869 grant on X3DNA-DSSR, an NIGMS National Resource for Structural Bioinformatics of Nucleic Acids

Created and maintained by Dr. Xiang-Jun Lu, Department of Biological Sciences, Columbia University