• CMI SEC-MALS system
  • CMI Jasco J815 CD instrument
  • CMI MST and ITC instruments
  • CMI SPR and BLI instruments
  • CMI Laboratory

Center for Macromolecular Interactions

Welcome to the Center for Macromolecular Interactions (CMI) in the department of Biological Chemistry and Molecular Pharmacology at Harvard Medical School.  Our mission is to enhance basic research in the HMS community by providing scientific consultation, training and access to shared biophysical instruments for the characterization and analysis of macromolecules and their complexes.

The facility currently includes instruments for Isothermal Titration Calorimetry (ITC), Surface Plasmon Resonance (SPR), Biolayer Interferometry (BLI), Differential Scanning Fluorimetry (DSF), Circular Dichroism (CD), Analytical Size Exclusion Chromatography for Multi-Angle Light Scattering (SEC-MALS) or Fluorescence detection (FSEC), and MicroScale Thermophoresis (MST).   To learn more about technologies available, go to the CMI Instruments Page.

 

Recent CMI User Publications

Li J, Su Y, Xia W, Qin Y, Humphries MJ, Vestweber D, Cabañas C, Lu C, Springer TA. Conformational equilibria and intrinsic affinities define integrin activation. EMBO J 2017;36(5):629-645.Abstract
We show that the three conformational states of integrin α5β1 have discrete free energies and define activation by measuring intrinsic affinities for ligand of each state and the equilibria linking them. The 5,000-fold higher affinity of the extended-open state than the bent-closed and extended-closed states demonstrates profound regulation of affinity. Free energy requirements for activation are defined with protein fragments and intact α5β1 On the surface of K562 cells, α5β1 is 99.8% bent-closed. Stabilization of the bent conformation by integrin transmembrane and cytoplasmic domains must be overcome by cellular energy input to stabilize extension. Following extension, headpiece opening is energetically favored. N-glycans and leg domains in each subunit that connect the ligand-binding head to the membrane repel or crowd one another and regulate conformational equilibria in favor of headpiece opening. The results suggest new principles for regulating signaling in the large class of receptors built from extracellular domains in tandem with single-span transmembrane domains.
Nasr ML, Baptista D, Strauss M, Sun Z-YJ, Grigoriu S, Huser S, Plückthun A, Hagn F, Walz T, Hogle JM, Wagner G. Covalently circularized nanodiscs for studying membrane proteins and viral entry. Nat Methods 2017;Abstract

We engineered covalently circularized nanodiscs (cNDs) which, compared with standard nanodiscs, exhibit enhanced stability, defined diameter sizes and tunable shapes. Reconstitution into cNDs enhanced the quality of nuclear magnetic resonance spectra for both VDAC-1, a β-barrel membrane protein, and the G-protein-coupled receptor NTR1, an α-helical membrane protein. In addition, we used cNDs to visualize how simple, nonenveloped viruses translocate their genomes across membranes to initiate infection.

Behrouzi R, Lu C, Currie MA, Jih G, Iglesias N, Moazed D. Heterochromatin assembly by interrupted Sir3 bridges across neighboring nucleosomes. Elife 2016;5Abstract

Heterochromatin is a conserved feature of eukaryotic chromosomes with central roles in regulation of gene expression and maintenance of genome stability. Heterochromatin formation involves spreading of chromatin-modifying factors away from initiation points over large DNA domains by poorly understood mechanisms. In Saccharomyces cerevisiae, heterochromatin formation requires the SIR complex, which contains subunits with histone-modifying, histone-binding, and self-association activities. Here, we analyze binding of the Sir proteins to reconstituted mono-, di-, tri-, and tetra-nucleosomal chromatin templates and show that key Sir-Sir interactions bridge only sites on different nucleosomes but not sites on the same nucleosome, and are therefore 'interrupted' with respect to sites on the same nucleosome. We observe maximal binding affinity and cooperativity to unmodified di-nucleosomes and propose that nucleosome pairs bearing unmodified histone H4-lysine16 and H3-lysine79 form the fundamental units of Sir chromatin binding and that cooperative binding requiring two appropriately modified nucleosomes mediates selective Sir recruitment and spreading.

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Latest News

Demo: SEC-MALS integrated HPLC control software

December 7, 2016

Wyatt has launched HPLC management software that integrates control of Agilent chromatography systems into Astra 7.  We'll be testing this software over the next few months.  Talk to Kelly if you'd like to try it.

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