Current Projects
Professor Bloomfield has closed his molecular biophysics research laboratory, and now focuses his efforts in two areas:
Public Engagement in Higher Education
Enhancing the University of Minnesotašs - and research-extensive universities as a whole - activities in public engagement.
Engagement is defined as the partnership of university knowledge and resources with those of the public and private sectors to enrich scholarship, research, and creative activity; enhance curriculum, teaching and learning; prepare educated, engaged citizens; strengthen democratic values and civic responsibility; address critical societal issues; and contribute to the public good.
Computer Tools for Education in Quantitative Biology
Developing powerful but easy-to-use tools for incorporating increasingly important quantitative, statistical, and physical approaches into biological and biochemical education.
Previous Major Research Projects
DNA Condensation by Multivalent Cations
The long-term objective is to understand the physical mechanism of DNA condensation
by multivalent cations, so as to comprehend the factors controlling compaction
in viruses and cells and in preparative and genetic engineering applications.
Understanding DNA condensation has two main aspects: equilibrium and kinetic
characterization of the condensation process, and elucidation of the forces
underlying condensation. DNA condensation seems to involve four major stages:
(1) initial rapid association of a few chains, (2) collapse of this complex
at some critical size, (3) growth of the critical nucleus by accretion,
and (4) long-time aggregation of fully-formed condensed particles to produce
larger particles. Each stage is reversible, but the process as a whole seems
to be nucleation-limited. The major energetic contributions to DNA condensation
are electrostatics, hydration, and distortions of the double helix. We are
currently engaged in experimental and theoretical studies of attractive
electrostatic mechanisms involving correlated counterion fluctuations, and
thermodynamics and statistical mechanics of preferential hydration. We are
also probing the effects of multivalent cations and protein binding on DNA through single molecule stretching with optical tweezers. We also use optical tweezers to study the overstretching transition of DNA, which appears to be a force-induced melting of the double helix.
Biopolymer Dynamics in Crowded Environments
DNA functions in crowded, strongly interacting solutions. The equilibrium
and dynamic aspects of its behavior are strongly influenced by its environment.
When the volume occupancy of a solution reaches several tens of percent,
as it does within cells, simple extrapolations from dilute solution behavior
become totally inadequate. Our goal in this project is to develop a solid
experimental and theoretical understanding of the ways in which high polymer
concentrations influence the diffusion of DNA, and of proteins which bind
to DNA. We feel that this should shed light on some important questions
in cell biology, such as the segregation of plasmids during cell division
in microorganisms, and the location by binding proteins of their specific
binding sites in a background of nonspecific DNA. To approach this goal,
we use fluorescence photobleaching recovery (FPR) as a major experimental
technique, and modern polymer theoretical concepts and computer simulation
as theoretical tools.
Recent Publications
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Last updated 12/11/05