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Insights in Biological and Synthetic Medicinal Chemistry

Larry H. Bernstein, M.D., FCAP, Curator

Leaders in Pharmaceutical Intelligence

Series E. 2;  10

Selected Articles Linking the Biological and Synthetic Worlds

The worlds of biological and synthetic chemistry both offer incredible diversity. Biology provides complex architectures including proteins, nucleic acids, and polysaccharides. Synthetic chemistry, on the other hand, provides a tool for atom-by-atom control over molecular structure that can be used to obtain molecules and materials inaccessible through biology.

In this ACS Select Virtual Issue, we highlight some of the recent advances in bioconjugation chemistry. These publications describe new strategies for functionalization of biomacromolecules, as well as the use of synthetic molecules as building blocks for assembly using biological machinery. The resultant conjugate systems have new and exciting properties, as demonstrated in new therapeutic and imaging applications.

– Vincent Rotello, Editor-in-Chief, Bioconjugate Chemistry
– C. Dale Poulter, Editor-in-Chief, The Journal of Organic Chemistry
– Amos Smith, III, Editor-in-Chief, Organic Letters

10.1  Bioconjugate Chemistry

10.1.1 Production of Site-Specific Antibody-Drug Conjugates Using Optimized Non-Natural Amino Acids in a Cell-Free Expression System
Zimmerman, E. S.; Heibeck, T. H.; Gill, A.; Li, X. F.; Murray, C. J.; Madlansacay, M. R.; Tran, C.; Uter, N. T.; Yin, G.; Rivers, P. J.; Yam, A. Y.; Wang, W. D.; Steiner, A. R.; Bajad, S. U.; Penta, K.; Yang, W. J.; Hallam, T. J.; Thanos, C. D.; Sato, A. K.
Bioconjugate Chem.201425 (2), pp 351-361
DOI: 10.1021/bc400490z

10.1.2 General Chemoselective and Redox-Responsive Ligation and Release Strategy
Park, S.; Westcott, N. P.; Luo, W.; Dutta, D.; Yousaf, M. N.
Bioconjugate Chem.201425 (3), pp 543-551
DOI: 10.1021/bc400565y

10.1.3 Chemoenzymatic Fc Glycosylation via Engineered Aldehyde Tags
Smith, E. L.; Giddens, J. P.; Iavarone, A. T.; Godula, K.; Wang, L. X.; Bertozzi, C. R.
Bioconjugate Chem.201425 (4), pp 788-795
DOI: 10.1021/bc500061s

10.1.4 Triazine-Based Tool Box for Developing Peptidic PET Imaging Probes: Syntheses, Microfluidic Radio labeling, and Structure-Activity Evaluation
Li, H. R.; Zhou, H. Y.; Krieger, S.; Parry, J. J.; Whittenberg, J. J.; Desai, A. V.; Rogers, B. E.; Kenis, P. J. A.; Reichert, D. E.
Bioconjugate Chem.201425 (4), pp 761-772
DOI: 10.1021/bc500034n

10.1.5 Developments in the Field of Bioorthogonal Bond Forming Reactions-Past and Present Trends
King, M.; Wagner, A.
Bioconjugate Chem.201425 (5), pp 825-839
DOI: 10.1021/bc500028d

10.1.6 Diels-Alder Cycloadditions on Synthetic RNA in Mammalian Cells
Pyka, A. M.; Domnick, C.; Braun, F.; Kath-Schorr, S.
Bioconjugate Chem.201425 (8), pp 1438-1443
DOI: 10.1021/bc500302y

10.1.7 High-Density Functionalization and Cross-Linking of DNA: “Click” and “Bis-Click” Cycloadditions Performed on Alkynylated Oligonucleotides with Fluorogenic Anthracene Azides
Pujari, S. S.; Ingale, S. A.; Seela, F.
Bioconjugate Chem.201425 (10), pp 1855-1870
DOI: 10.1021/bc5003532

10.1.8 Surface Functionalization of Exosomes Using Click Chemistry
Smyth, T.; Petrova, K.; Payton, N. M.; Persaud, I.; Redzic, J. S.; Gruner, M. W.; Smith-Jones, P.; Anchordoquy, T. J.
Bioconjugate Chem.201425 (10), pp 1777-1784
DOI: 10.1021/bc500291r

10.1.9 Site-Specific Antibody-Drug Conjugates: The Nexus of Biciorthogonal Chemistry, Protein Engineering, and Drug Development.
Agarwal, P.; Bertozzi, C. R.
Bioconjugate Chem.201526 (2), pp 176-192
DOI: 10.1021/bc5004982

10.1.10 Strain-Promoted Oxidation-Controlled Cyclooctyne-1,2-Quinone Cycloaddition (SPOCQ) for Fast and Activatable Protein Conjugation
Borrmann, A.; Fatunsin, O.; Dommerholt, J.; Jonker, A. M.; Lowik, D.; van Hest, J. C. M.; van Delft, F. L.
Bioconjugate Chem.201526 (2), pp 257-261
DOI: 10.1021/bc500534d

10.2 The Journal of Organic Chemistry

10.2.1 Sequential “Click” – “Photo-Click” Cross-Linker for Catalyst-Free Ligation of Azide-Tagged Substrates
Arumugam, S.; Popik, V. V.
J. Org. Chem.201479 (6), pp 2702-2708
DOI: 10.1021/jo500143v

10.2.3 Diazirine-Containing RNA Photo-Cross-Linking Probes for Capturing microRNA Targets
Nakamoto, K.; Ueno, Y.
J. Org. Chem.201479 (6), pp 2463-2472
DOI: 10.1021/jo402738t

10.2.4 Interstrand Cross-Link and Bioconjugate Formation in RNA from a Modified Nucleotide
Sloane, J. L.; Greenberg, M. M.
J. Org. Chem.201479 (20), pp 9792-9798
DOI: 10.1021/jo501982r

10.2.5 Synthesis of Base-Modified 2 ‘-Deoxyribonucleoside Triphosphates and Their Use in Enzymatic Synthesis of Modified DNA for Applications in Bioanalysis and Chemical Biology
Hocek, M.
J. Org. Chem.201479 (21), pp 9914-9921
DOI: 10.1021/jo5020799

10.2.6 Site-specific PEGylation of Proteins: Recent Developments
Nischan, N.; Hackenberger, C. P. R.
J. Org. Chem.201479 (22), pp 10727-10733
DOI: 10.1021/jo502136n

10.3 Organic Letters

10.3.1 One-Pot Peptide Ligation-Desulfurization at Glutamate
Cergol, K. M.; Thompson, R. E.; Malins, L. R.; Turner, P.; Payne, R. J.
Org. Lett.201416 (1), pp 290-293
DOI: 10.1021/ol403288n

10.3.2 Semisynthesis of Peptoid-Protein Hybrids by Chemical Ligation at Serine
Levine, P. M.; Craven, T. W.; Bonneau, R.; Kirshenbaum, K
Org. Lett.201416 (2), pp 512-515
DOI: 10.1021/ol4033978

10.3.3 A Photoinduced, Benzyne Click Reaction
Gann, A. W.; Amoroso, J. W.; Einck, V. J.; Rice, W. P.; Chambers, J. J.; Schnarr, N. A.
Org. Lett.201416 (7), pp 2003-2005
DOI: 10.1021/ol500389t

10.3.4 Amine-Selective Bioconjugation Using Arene Diazonium Salts
Diethelm, S.; Schafroth, M. A.; Carreira, E. M.
Org. Lett.201416 (15), pp 3908-3911
DOI: 10.1021/ol5016509

10.3 5 Efficient and Facile Synthesis of Acrylamide Libraries for Protein-Guided Tethering
Allen, C. E.; Curran, P. R.; Brearley, A. S.; Boissel, V.; Sviridenko, L.; Press, N. J.; Stonehouse, J. P.; Armstrong, A.
Org. Lett.201517 (3), pp 458-460
DOI: 10.1021/ol503486t

10.4 Synthesis, Design and Molecular Function

This Special Issue on “Synthesis, Design and Molecular Function”, guest-edited by Paul Wender, is intended to explore the many exciting new advances and challenges associated with designing and making molecules in the 21st century. It features contributions from thought leaders in the field directed at new reactions, reagents and catalysts, process technologies and screening strategies.

See guest editorial by Paul Wender

10.4.1 Art, Architecture, and the Molecular Frontier
Paul A. Wender (Guest Editor)
DOI10.1021/acs.accounts.5b00332

10.4.2 From Synthesis to Function via Iterative Assembly of N-Methyliminodiacetic Acid Boronate Building Blocks
Junqi Li, Anthony S. Grillo, and Martin D. Burke *
DOI10.1021/acs.accounts.5b00128

10.4.3 Trimethylenemethane Diyl Mediated Tandem Cycloaddition Reactions: Mechanism Based Design of Synthetic Strategies
Hee-Yoon Lee *
DOI10.1021/acs.accounts.5b00178

10.4.4 Intermolecular Reaction Screening as a Tool for Reaction Evaluation
Karl D. Collins* and Frank Glorius*
DOI10.1021/ar500434f

10.4.5 Development of Globo-H Cancer Vaccine
Samuel J. Danishefsky*, Youe-Kong Shue, Michael N. Chang, and Chi-Huey Wong*
DOI10.1021/ar5004187

10.4.6 Total Synthesis of Vinblastine, Related Natural Products, and Key Analogues and Development of Inspired Methodology Suitable for the Systematic Study of Their Structure–Function Properties
Justin E. Sears and Dale L. Boger*
DOI10.1021/ar500400w

10.4.7 Reaction Design, Discovery, and Development as a Foundation to Function-Oriented Synthesis
Glenn C. Micalizio* and Sarah B. Hale
DOI10.1021/ar500408e

10.4.8 Copy, Edit, and Paste: Natural Product Approaches to Biomaterials and Neuroengineering
Karl Gademann*
DOI10.1021/ar500435b

10.4.9 Catalytic Enantioselective Construction of Quaternary Stereocenters: Assembly of Key Building Blocks for the Synthesis of Biologically Active Molecules
Yiyang Liu, Seo-Jung Han, Wen-Bo Liu, and Brian M. Stoltz*
DOI10.1021/ar5004658

10.4.10 Focused Library with a Core Structure Extracted from Natural Products and Modified: Application to Phosphatase Inhibitors and Several Biochemical Findings
Go Hirai* and Mikiko Sodeoka*
DOI10.1021/acs.accounts.5b00048

10.5 Ionization Methods in Mass Spectrometry

Mass spectrometry has undoubtedly boomed over the last two decades and has become a major analytical tool in many disciplines. The technique relies on the separation of ions of different m/z, and its success hinges on efficient ionization methods that furthermore should be tailored to the task at hand. Depending on the application, ionization should be soft, hard, selective, as efficient as possible, etc. This virtual issue pulls together publications from Analytical Chemistry that showcase the exemplary developments in ionization techniques.

10.5.1 From the editorial by Renato Zenobi
DOI 10.1021/acs.analchem.5b01062

10.5.2 Nanophotonic Ionization for Ultratrace and Single-Cell Analysis by Mass Spectrometry
Bennett N. Walker, Jessica A. Stolee, and Akos Vertes
DOI: 10.1021/ac301238k

10.5.3 Unraveling the Mechanism of Electrospray Ionization
Lars Konermann, Elias Ahadi, Antony D. Rodriguez, and Siavash Vahidi
DOI: 10.1021/ac302789c

10.5.4 Ambient Surface Mass Spectrometry Using Plasma-Assisted Desorption Ionization: Effects and Optimization of Analytical Parameters for Signal Intensities of Molecules and Polymers
T. L. Salter, I. S. Gilmore, A. Bowfield, O. T. Olabanji, and J. W. Bradley
DOI: 10.1021/ac302677m

10.5.5 Fast Surface Acoustic Wave-Matrix-Assisted Laser Desorption Ionization Mass Spectrometry of Cell Response from Islets of Langerhans
Loreta Bllaci, Sven Kjellström, Lena Eliasson, James R. Friend, Leslie Y. Yeo, and Staffan Nilsson
DOI: 10.1021/ac3019125

10.5.6 Electrospun Nanofibers as Substrates for Surface-Assisted Laser Desorption/Ionization and Matrix-Enhanced Surface-Assisted Laser Desorption/Ionization Mass Spectrometry
Tian Lu and Susan V. Olesik
DOI: 10.1021/ac303292e

10.5.7 Capillary Photoionization: A High Sensitivity Ionization Method for Mass Spectrometry
Markus Haapala, Tina Suominen, and Risto Kostiainen
DOI: 10.1021/ac4002673

10.5.8 High-Speed Tandem Mass Spectrometric in Situ Imaging by Nanospray Desorption Electrospray Ionization Mass Spectrometry
Ingela Lanekoff, Kristin Burnum-Johnson, Mathew Thomas, Joshua Short, James P. Carson, Jeeyeon Cha, Sudhansu K. Dey, Pengxiang Yang, Maria C. Prieto Conaway, and Julia Laskin
DOI: 10.1021/ac401760s

10.5.9 Atomic Force Microscope Controlled Topographical Imaging and Proximal Probe Thermal Desorption/Ionization Mass Spectrometry Imaging
Olga S. Ovchinnikova, Kevin Kjoller, Gregory B. Hurst, Dale A. Pelletier, and Gary J. Van Berkel
DOI: 10.1021/ac4026576

10.5.10 Droplet Electrospray Ionization Mass Spectrometry for High Throughput Screening for Enzyme Inhibitors
Shuwen Sun and Robert T. Kennedy
DOI: 10.1021/ac502542z

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Introduction to Translational Medicine (TM) – Part 1: Translational Medicine


Introduction to Translational Medicine (TM) – Part 1: Translational Medicine

Author and Curator: Larry H Bernstein, MD, FCAP

and

Curator: Aviva Lev-Ari, PhD, RN 

 

This document in the Series A: Cardiovascular Diseases e-Series Volume 4: Translational and Regenerative Medicine,  is a measure of the postgenomic and proteomic advances in the laboratory to the practice of clinical medicine.  The Chapters are preceded by several videos by prominent figures in the emergence of this transformative change.  When I was a medical student, a large body of the current language and technology that has extended the practice of medicine did not exist, but a new foundation, predicated on the principles of modern medical education set forth by Abraham Flexner, was sprouting.  The highlights of this evolution were:

  • Requirement for premedical education in biology, organic chemistry, physics, and genetics.
  • Medical education included two years of basic science education in anatomy, physiology, pharmacology, and pathology prior to introduction into the clinical course sequence of the last two years.
  • Post medical graduate education was an internship year followed by residency in pediatrics, OBGyn, internal medicine, general surgery, psychiatry, neurology, neurosurgery, pathology, radiology, and anesthesiology, emergency medicine.
  • Academic teaching centers were developing subspecialty centers in ophthalmology, ENT and head and neck surgery, cardiology and cardiothoracic surgery, and hematology, hematology/oncology, and neurology.
  • The expansion of postgraduate medical programs included significant postgraduate funding for programs by the National Institutes of Health, and the NIH had faculty development support in a system of peer-reviewed research grant programs in medical and allied sciences.

The period after the late 1980s saw a rapid expansion of research in genomics and drug development to treat emerging threats of infectious diseases as US had a large worldwide involvement after the end of the Vietnam War, and drug resistance was increasingly encountered (malaria, tick borne diseases, salmonellosis, pseudomonas aeruginosa, staphylococcus aureus, etc.).

Moreover, the post-millenium found a large, dwindling population of veterans who had served in WWII and Vietnam, and cardiovascular, musculoskeletal,  dementias, and cancer were now more common.  The Human Genome Project was undertaken to realign the existing knowledge of gene structure and genetic regulation with the needs for drug development, which was languishing in development failures due to unexpected toxicities.

A substantial disconnect existed between diagnostics and pharmaceutical development, which had been over-reliant on modification of known organic structures to increase potency and reduce toxicity.  This was about to change with changes in medical curricula, changes in residency programs and physicians cross-training in disciplines, and the emergence of bio-pharma, based on the emerging knowledge of the cell function, and at the same time, the medical profession was developing an evidence-base for therapeutics, and more pressure was placed on informed decision-making.

The great improvement in proteomics came from GCLC/MS-MS and is described in the video interview with Dr. Gyorgy Marko-Varga, Sweden, in video 1 of 3 (Advancing Translational Medicine).  This is a discussion that is focused on functional proteomics role in future diagnostics and therapy, involving a greater degree of accuracy in mass spectrometry (MS) than can be obtained by antibody-ligand binding, and is illustrated below, the last emphasizing the importance of information technology and predictive analytics

Thermo ScientificImmunoassays and LC–MS/MS have emerged as the two main approaches for quantifying peptides and proteins in biological samples. ELISA kits are available for quantification, but inherently lack the discriminative power to resolve isoforms and PTMs.

To address this issue we have developed and applied a mass spectrometry immunoassay–selected reaction monitoring (Thermo Scientific™ MSIA™ SRM technology) research method to quantify PCSK9 (and PTMs), a key player in the regulation of circulating low density lipoprotein cholesterol (LDL-C).

A Day in the (Future) Life of a Predictive Analytics Scientist

 

By Lars Rinnan, CEO, NextBridge   April 22, 2014

A look into a normal day in the near future, where predictive analytics is everywhere, incorporated in everything from household appliances to wearable computing devices.

During the test drive (of an automobile), the extreme acceleration makes your heart beat so fast that your personal health data sensor triggers an alarm. The health data sensor is integrated into the strap of your wrist watch. This data is transferred to your health insurance company, so you say a prayer that their data scientists are clever enough to exclude these abnormal values from your otherwise impressive health data. Based on such data, your health insurance company’s consulting unit regularly gives you advice about diet, exercise, and sleep. You have followed their advice in the past, and your performance has increased, which automatically reduced your insurance premiums. Win-win, you think to yourself, as you park the car, and decide to buy it.

In the clinical presentation at Harlan Krumholtz’ Yale Symposium, Prof. Robert Califf, Director of the Duke University Translational medicine Clinical Research Institute, defines translational medicine as effective translation of science to clinical medicine in two segments:

  1. Adherence to current standards
  2. Improving the enterprise by translating knowledge

He says that discrepancies between outcomes and medical science will bridge a gap in translation by traversing two parallel systems.

  1. Physician-health organization
  2. Personalized medicine

He emphasizes that the new basis for physician standards will be legitimized in the following:

  1. Comparative effectiveness (Krumholtz)
  2. Accountability

Some of these points are repeated below:

WATCH VIDEOS ON YOUTUBE

https://www.youtube.com/watch?v=JFdJRh9ZPps#t=678  Harlan Krumholtz

https://www.youtube.com/watch?v=JFdJRh9ZPps#t=678  complexity

https://www.youtube.com/watch?v=JFdJRh9ZPps#t=678  integration map

https://www.youtube.com/watch?v=JFdJRh9ZPps#t=678  progression

https://www.youtube.com/watch?v=JFdJRh9ZPps#t=678  informatics

An interesting sidebar to the scientific medical advances is the huge shift in pressure on an insurance system that has coexisted with a public system in Medicare and Medicaid, initially introduced by the health insurance industry for worker benefits (Kaiser, IBM, Rockefeller), and we are undertaking a formidable change in the ACA.

The current reality is that actuarially, the twin system that has existed was unsustainable in the long term because it is necessary to have a very large pool of the population to spread the costs, and in addition, the cost of pharmaceutical development has driven consolidation in the industry, and has relied on the successes from public and privately funded research.

https://www.youtube.com/watch?v=X6J_7PvWoMw#t=57  Corbett Report Nov 2013

(1979 ER Brown)  UCPress  Rockefeller Medicine Men

https://www.youtube.com/watch?v=X6J_7PvWoMw#t=57   Liz Fowler VP of Wellpoint (designed ACA)

I shall digress for a moment and insert a video history of DNA, that hits the high points very well, and is quite explanatory of the genomic revolution in medical science, biology, infectious disease and microbial antibiotic resistance, virology, stem cell biology, and the undeniability of evolution.

DNA History

https://www.youtube.com/watch?v=UUDzN4w8mKI&list=UUoHRSQ0ahscV14hlmPabkVQ

As I have noted above, genomics is necessary, but not sufficient.  The story began as replication of the genetic code, which accounted for variation, but the accounting for regulation of the cell and for metabolic processes was, and remains in the domain of an essential library of proteins. Moreover, the functional activity of proteins, at least but not only if they are catalytic, shows structural variants that is characterized by small differences in some amino acids that allow for separation by net charge and have an effect on protein-protein and other interactions.

Protein chemistry is so different from DNA chemistry that it is quite safe to consider that DNA in the nucleotide sequence does no more than establish the order of amino acids in proteins. On the other hand, proteins that we know so little about their function and regulation, do everything that matters including to set what and when to read something in the DNA.

Jose Eduardo de Salles Roselino

Chapters 2, 3, and 4 sequentially examine:

  • The causes and etiologies of cardiovascular diseases
  • The diagnosis, prognosis and risks determined by – biomarkers in serum, circulating cells, and solid tissue by contrast radiography
  • Treatment of cardiovascular diseases by translation of science from bench to bedside, including interventional cardiology and surgical repair

These are systematically examined within a framework of:

  • Genomics
  • Proteomics
  • Cardiac and Vascular Signaling
  • Platelet and Endothelial Signaling
  • Cell-protein interactions
  • Protein-protein interactions
  • Post-Translational Modifications (PTMs)
  • Epigenetics
  • Noncoding RNAs and regulatory considerations
  • Metabolomics (the metabolome)
  • Mitochondria and oxidative stress

 

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World of Metabolites:  Lawrence Berkeley National Laboratory developed Imaging Technique for their Capturing

Reporter: Aviva Lev-Ari, PhD, RN

 

UPDATED on 9/27/2017

From: “Dr. Larry Bernstein” <larry.bernstein@gmail.com>

Reply-To: “Dr. Larry Bernstein” <larry.bernstein@gmail.com>

Date: Tuesday, September 26, 2017 at 10:45 AM

To: Aviva Lev-Ari <AvivaLev-Ari@alum.berkeley.edu>

Precision or personalized medicine seeks to provide the right drug to the right patient at the right time. Hence the significance of the principal omics: disciplines of genomics, proteomics, and last but not least metabolomics, as diagnostic enablers. 

Primacy among the ‘omics is debatable, but the notion that metabolomics reflects the most accurate picture of disease states has reached significant momentum. “Almost every factor affecting health exerts its influence by altering metabolite levels,” says Mike Milburn, Ph.D., Chief Scientific Officer at Metabolon (Morrisville, North Carolina, USA). 

Where clinical chemistry blood tests typically quantify individual species for example, glucose or cholesterol, metabolomics measures hundreds or even thousands of metabolites to provide a nuanced view of disease states. 

Metabolon employs standard liquid chromatography-mass spectrometry (LC-MS) for metabolomic studies. Its proprietary informatics and processing platform, Precision MetabolomicsTM, overcomes the “big data” challenge, a natural consequence of measuring hundreds or thousands of small-molecule entities with widely differing concentrations in a single sample. Precision Metabolomics enables “n of 1” studies — meaningful clinical trials on a single patient, Milburn adds:

Diagnostic metabolomics resembles other medical testing, where results are compared against readings from healthy individuals or a reference population. Many metabolites serve that purpose but none on its own is sufficiently specific or diagnostic for a diagnosis — otherwise it would comprise a standalone test. Hence the reliance on metabolite panels or networks, which together may provide a clearer view of disease states than any single diagnostic molecule.

 

Imaging technique captures ever-changing world of metabolites

Thu, 06/13/2013 – 7:38am

The kinetic world of metabolites comes to life in this merged overlay of mass spectrometry images. It shows new versus pre-existing metabolites in a tumor section (yellow and red indicate newer metabolites). Image: Lawrence Berkeley National LaboratoryThe kinetic world of metabolites comes to life in this merged overlay of mass spectrometry images. It shows new versus pre-existing metabolites in a tumor section (yellow and red indicate newer metabolites). Image: Lawrence Berkeley National LaboratoryWhat would you do with a camera that can take a picture of something and tell you how new it is? If you’re Lawrence Berkeley National Laboratory scientists Katherine Louie, Ben Bowen, Jian-Hua Mao and Trent Northen, you use it to gain a better understanding of the ever-changing world of metabolites, the molecules that drive life-sustaining chemical transformations within cells.

They’re part of a team of researchers that developed a mass spectrometry imaging technique that not only maps the whereabouts of individual metabolites in a biological sample, but how new the metabolites are too.

That’s a big milestone, because metabolites are constantly in flux. They’re synthesized on-demand in order to sustain an organism’s energy requirements. When you eat lunch, metabolites momentarily fire up in various cell populations throughout your body to fuel your day. But they also have a dark side. Cancer cells tap metabolites to drive tumor development.

Unfortunately, the current ways to clinically analyze metabolites don’t capture their kinetics. Microscopy maps the cells and biomarkers in a tumor section. And traditional mass spectrometry reveals the abundance and spatial distribution of molecules such as metabolites.

But these images are static snapshots of a highly dynamic process. They’re blind to how recently the metabolites were synthesized, which is a key piece of information. The metabolic status of a cell population is a good indicator of what the cells were up to when the sample was taken.

To image the ebb and flow of metabolites, the scientists paired mass spectrometry with a clinically accepted way to label tissue that uses a hydrogen isotope called deuterium.

As reported in Nature Scientific Reports, they administered deuterium to mice with tumors. Newly synthesized lipids (a hallmark of metabolic activity) became labeled with deuterium, while pre-existing lipids remained unlabeled. The scientists then removed tumor sections and analyzed them with a type of mass spectrometry.

The resulting images look like freeze-frames of a slow-motion fireworks show. They reveal when and where metabolic turnover occurs in a tumor section, with the brighter colors depicting newly synthesized lipids.

The scientists also found that regions with new lipids had a higher tumor grade, which is a good predictor of how quickly a tumor is likely to grow.

“Our approach, called kinetic mass spectrometry imaging, could provide clinicians with quantifiable information they can use,” says Bowen.

The scientists are now applying their imaging technique to study metabolic flux in other biological systems, such as microbial communities.

Source: Lawrence Berkeley National Laboratory

http://www.rdmag.com/news/2013/06/imaging-technique-captures-ever-changing-world-metabolites?et_cid=3310531&et_rid=461755519&location=top

 

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