About

Sarah L. Keller is a biophysicist and the Duane and Barbara LaViolette Endowed Professor of Chemistry at the University of Washington. She investigates self-assembling soft condensed matter systems, with a primary research focus on how lipid mixtures within bilayer membranes give rise to complex phase behavior and how this behavior manifests in biological membranes. Keller earned her Ph.D. in Physics from Princeton University in 1995 and completed postdoctoral research as a Presidential Fellow at UC Santa Barbara and as an NIH NRSA Fellow at Stanford University. Her work has significantly contributed to understanding membrane organization and phase separation, which are fundamental to cellular function.

Research topics

• Biochemistry
• Chemistry
• Biology
• Biophysics
• Organic chemistry
• Engineering
• Physics
• Cell biology
• Biomedical engineering
• Optics
• Nuclear magnetic resonance
• Materials science
• Nanotechnology

Selected publications

• BPS2026 – Temperature at which yeast vacuole membranes undergo liquid-liquid phase separation as a function of time in the stationary stage (Tmix vs time)

  Biophysical Journal · 2026-02-01

  articleSenior author
  PublisherDOI

• BPS2026 – Wrinkling in sheets with nonuniform growth and bending rigidity

  Biophysical Journal · 2026-02-01

  articleSenior author
  PublisherDOI

• Wrinkling in Sheets with Nonuniform Growth and Bending Rigidity

  ArXiv.org · 2025-11-14

  preprintOpen accessSenior author

  Thin elastic sheets bend easily, leading to mechanical instabilities such as wrinkling. Here, we investigate wrinkles at edges of bi-strips, which consist of two thin sheets, one that swells and one that does not, joined side-by-side. It is well known that when bending rigidity is uniform across an isolated bi-strip, swelling results in axisymmetric shapes like a wine bottle: two cylinders of different radii are joined by a smooth transition zone. However, when the bending rigidity of the swollen sheet differs from that of the non-swollen sheet, purely axisymmetric shapes are no longer energetically favorable, and wrinkles arise. When the bending rigidity of the non-swollen sheet is essentially infinite, the wrinkles coarsen with distance from the transition zone such that dimensionless wavelengths and widths are related by $\tildeλ \propto \tilde{w}^{2/3}$. If the bending rigidity of the non-swollen sheet is non-infinite (but~still significantly larger than that of the swollen sheet), then the non-swollen sheet assumes a non-infinite radius of curvature, $R_0$. We find that the wrinkles in this system extend a critical distance, $w_C$, beyond the junction of the two strips and that $w_C \propto R_0$. Local undulations of wrinkles are favorable in this system because they decrease the overall bending energy by allowing the non-swollen sheet to have a larger radius of curvature than would otherwise be dictated by its reference geometry. Our results are relevant to a wide range of sheets that experience non-uniform growth, whether in natural systems such as plants or in synthetic systems such as designed, responsive materials.

  PublisherOA PDFDOI

• BPS2025 - Impact of replicative age on liquid-liquid phase separation in the yeast vacuole membrane

  Biophysical Journal · 2025-02-01

  articleSenior author
  PublisherDOI

• Micron-scale, liquid-liquid phase separation in ternary lipid membranes containing DPPE

  Biophysical Journal · 2025-09-13

  articleOpen accessSenior author
  PublisherOA PDFDOI

• BPS2025 - Giant vesicles containing DiphyPC, PE-lipids, and cholesterol exhibit 3-phase coexistence and solid phases that persist at high temperatures

  Biophysical Journal · 2025-02-01

  articleSenior author
  PublisherDOI

• Several common methods of making vesicles (except an emulsion method) capture intended lipid ratios

  Biophysical Journal · 2025-04-05 · 1 citations

  erratumSenior author
  PublisherDOI

• Micron-scale, liquid-liquid phase separation in ternary lipid membranes containing DPPE

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-05-09 · 1 citations

  preprintOpen accessSenior authorCorresponding

  Micron-scale, liquid-liquid phase separation occurs in membranes of living cells, with physiological consequences. To discover which lipids might support phase separation in cell membranes and how lipids might partition between phases, miscibility phase diagrams have been mapped for model membranes. Typically, model membranes are composed of ternary mixtures of a lipid with a high melting temperature, a lipid with a low melting temperature, and cholesterol. Phospholipids in ternary mixtures are chosen primarily to favor stable membranes (phosphatidylcholines and sphingomyelins) or add charge (phosphatidylglycerols and phosphatidylserines). A major class of phospholipids missing from experimental ternary diagrams has been the phosphatidylethanolamines (PEs). PE-lipids constitute up to 20 mol% of common biological membranes, where they influence protein function and facilitate membrane fusion. These biological effects are often attributed to PE's smaller headgroup, which leads to higher monolayer spontaneous curvatures and higher melting temperatures. Taken alone, the higher melting points of saturated PE-lipids imply that liquid-liquid phase separation should persist to higher temperatures in membranes containing PE-lipids. Here, we tested that hypothesis by substituting a saturated PE-lipid (DPPE) for its corresponding PC-lipid (DPPC) in two well-studied ternary membranes (DOPC/DPPC/cholesterol and DiphyPC/DPPC/cholesterol). We used fluorescence microscopy to map full ternary phase diagrams for giant vesicles over a range of temperatures. Surprisingly, we found no micron-scale, liquid-liquid phase separation in vesicles of the first mixture (DOPC/DPPE/cholesterol), and only a small region of liquid-liquid phase separation in the second mixture (DiphyPC/DPPE/cholesterol). Instead, coexisting solid and liquid phases were widespread, with the solid phase enriched in DPPE. An unusual feature of these ternary membranes is that solid and liquid-ordered phases can be distinguished by fluorescence microscopy, so tie-line directions can be estimated throughout the phase diagram, and transition temperatures to the 3-phase region (containing a liquid-disordered phase, a liquid-ordered phase, and a solid phase) can be accurately measured.

  PublisherOA PDFDOI

• BPS2025 - Mapping phase diagrams for ternary vesicle compositions with PE lipids

  Biophysical Journal · 2025-02-01

  articleSenior author
  PublisherDOI

• A case report of recurrent ovarian torsion following oocyte cryopreservation managed with dual technique oophoropexy

  Journal of Case Reports and Images in Obstetrics and Gynecology · 2024-05-28

  articleOpen access

  Introduction: Ovarian torsion is a known risk of ovarian hyperstimulation done as part of fertility treatments. The purpose of this case report is to describe an unusual case of recurrent ovarian torsion following oocyte cryopreservation that was ultimately managed with ovarian detorsion and dual technique oophoropexy. Case Report: The patient presented is a 25-yearold female with history of recurrent ovarian torsion who underwent fertility preservation with ovarian cryopreservation in the setting of risk for ovarian loss in the case of recurrent torsion episodes. Following ovarian hyperstimulation and oocyte retrieval, the patient experienced three recurrent episodes of torsion which were surgically managed. On the third episode, a dual technique oophoropexy was performed using both utero-ovarian ligament plication and ovarian fixation. Conclusion: This case describes an unusual presentation of an uncommon complication of ovarian stimulation. During her surgical management of recurrent ovarian torsion, ovarian conservation was prioritized and a dual oophoropexy technique was utilized which has thus far prevented further recurrent episodes of torsion.

  PublisherOA PDFDOI

Recent grants

• CAREER: Lateral Phase Separation of Rafts and Liquid Domains in Lipid Systems

  NSF · $657k · 2002–2008

• Leveraging 2D and 3D interactions to understand structural transitions in model and cell membranes from molecular to micron scales

  NSF · $900k · 2019–2025

• Fundamental measurements of liquid-liquid phase separation in lipid membranes and development of methods to assay domain compositions

  NSF · $1.2M · 2023–2027

• Transforming fundamental biological questions about cell membranes into quantitative experiments using model and cell systems

  NSF · $1.3M · 2014–2021

• Biophysical Measurements of Lipid Membranes to Investigate Miscibility, Critical Points, and Sterol Solubility

  NSF · $852k · 2008–2015

Frequent coauthors

• Caitlin E. Cornell

  University of California, Berkeley

  34 shared

• Aurelia R. Honerkamp‐Smith

  Lehigh University

  21 shared

• Sarah L. Veatch

  University of Michigan–Ann Arbor

  19 shared

• Roy A. Black

  University of Washington

  17 shared

• Matthew C. Blosser

  University of Southern California

  17 shared

• Alexey J. Merz

  University of Washington

  14 shared

• Valerie S. Ratts

  13 shared

• Zachary R. Cohen

  University of Washington

  13 shared

Labs

• Keller LabPI

Education

• Ph.D., Physics

  Princeton University

• Other

  UC Santa Barbara

• Other

  Stanford University

Awards & honors

• AWIS Award for Science Advancement and Leadership, 2025
• Fellow of the Biophysical Society, 2021
• Honorable Mention – UW Distinguished Graduate Mentor Award,…
• Cottrell STAR Award, 2019
• Avanti Award (renamed the Agnes Pockels Award), Biophysical…