Sperm Trajectories Form Chiral Ribbons

• Ting-Wei Su,
• Inkyum Choi,
• Jiawen Feng,
• Kalvin Huang,
• Euan McLeod
• & Aydogan Ozcan

• Scientific Reports
   
  3,
   
  Article number:
   
  1664
   
  doi:10.1038/srep01664

• We report the discovery of an entirely new three-dimensional (3D) swimming pattern observed in human and horse sperms. This motion is in the form of ‘chiral ribbons’, where the planar swing of the sperm head occurs on an osculating plane creating in some cases a helical ribbon and in some others a twisted ribbon. The latter, i.e., the twisted ribbon trajectory, also defines a minimal surface, exhibiting zero mean curvature for all the points on its surface. These chiral ribbon swimming patterns cannot be represented or understood by already known patterns of sperms or other micro-swimmers. The discovery of these unique patterns is enabled by holographic on-chip imaging of >33,700 sperm trajectories at >90–140 frames/sec, which revealed that only ~1.7% of human sperms exhibit chiral ribbons, whereas it increases to ~27.3% for horse sperms. These results might shed more light onto the statistics and biophysics of various micro-swimmers' 3D motion.

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Droplet Detachment by Air Flow for Microstructured SuperhydrophobicSurfaces

Pengfei Hao *, Cunjing Lv , and Zhaohui Yao
Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
Langmuir, Article ASAP
DOI: 10.1021/la400187c
Publication Date (Web): April 4, 2013
Copyright © 2013 American Chemical Society

http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/0/langd5.ahead-of-print/la400187c/aop/images/medium/la-2013-00187c_0008.gif

Quantitative correlation between critical air velocity and roughness of microstructured surface has still not been established systematically until the present; the dynamics of water droplet detachment by air flow from micropillar-like superhydrophobic surfaces is investigated by combining experiments and simulation comparisons. Experimental evidence demonstrates that the onset of water droplet detachment from horizontal micropillar-like superhydrophobic surfaces under air flow always starts with detachment of the rear contact lines of the droplets from the pillar tops, which exhibits a similar dynamic mechanism for water droplet motion under a gravity field. On the basis of theoretical analysis and numerical simulation, an explicit analytical model is proposed for investigating the detaching mechanism, in which the critical air velocity can be fully determined by several intrinsic parameters: water–solid interface area fraction, droplet volume, and Young’s contact angle. This model gives predictions of the critical detachment velocity of air flow that agree well with the experimental measurements.

Neurons and other parts of brain vidualized

See through brains

Bilayer Thickness Mismatch Controls Domain Size in Model Membranes

J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/ja3113615
Publication Date (Web): February 7, 2013
Copyright © 2013 American Chemical Society

Frederick A. Heberle *†, Robin S. Petruzielo §, Jianjun Pan †, Paul Drazba , Norbert Kučerka □, Robert F. Standaert †‡#, Gerald W. Feigenson , and John Katsaras *†◊
†Biology & Soft Matter and ‡Biosciences Divisions, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States

The observation of lateral phase separation in lipid bilayers has received considerable attention, especially in connection to lipid raft phenomena in cells. It is widely accepted that rafts play a central role in cellular processes, notably signal transduction. While micrometer-sized domains are observed with some model membrane mixtures, rafts much smaller than 100 nm—beyond the reach of optical microscopy—are now thought to exist, both in vitro and in vivo. We have used small-angle neutron scattering, a probe free technique, to measure the size of nanoscopic membrane domains in unilamellar vesicles with unprecedented accuracy. These experiments were performed using a four-component model system containing fixed proportions of cholesterol and the saturated phospholipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), mixed with varying amounts of the unsaturated phospholipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We find that liquid domain size increases with the extent of acyl chain unsaturation (DOPC:POPC ratio). Furthermore, we find a direct correlation between domain size and the mismatch in bilayer thickness of the coexisting liquid-ordered and liquid-disordered phases, suggesting a dominant role for line tension in controlling domain size. While this result is expected from line tension theories, we provide the first experimental verification in free-floating bilayers. Importantly, we also find that changes in bilayer thickness, which accompany changes in the degree of lipid chain unsaturation, are entirely confined to the disordered phase. Together, these results suggest how the size of functional domains in homeothermic cells may be regulated through changes in lipid composition.

Scientist find exoplanet that contains water and Carbon dioxide

Published Online March 14 2013
Science 22 March 2013:
Vol. 339 no. 6126 pp. 1398-1401
DOI: 10.1126/science.1232003

Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere


Determining the atmospheric structure and chemical composition of an exoplanet remains a formidable goal. Fortunately, advancements in the study of exoplanets and their atmospheres have come in the form of direct imaging—spatially resolving the planet from its parent star—which enables high-resolution spectroscopy of self-luminous planets in jovian-like orbits. Here, we present a spectrum with numerous, well-resolved molecular lines from both water and carbon monoxide from a massive planet orbiting less than 40 astronomical units from the star HR 8799. These data reveal the planet’s chemical composition, atmospheric structure, and surface gravity, confirming that it is indeed a young planet. The spectral lines suggest an atmospheric carbon-to-oxygen ratio that is greater than that of the host star, providing hints about the planet’s formation.

http://www.sciencemag.org/content/339/6126/1398.full

Ultrafast Tryptophan-to-Heme Electron Transfer in Myoglobins Revealed by UV 2D Spectroscopy

Published Online February 7 2013
Science 29 March 2013:
Vol. 339 no. 6127 pp. 1586-1589
DOI: 10.1126/science.1230758

1Laboratory of Ultrafast Spectroscopy, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.

Tryptophan is commonly used to study protein structure and dynamics, such as protein folding, as a donor in fluorescence resonant energy transfer (FRET) studies. By using ultra-broadband ultrafast two-dimensional (2D) spectroscopy in the ultraviolet (UV) and transient absorption in the visible range, we have disentangled the excited state decay pathways of the tryptophan amino acid residues in ferric myoglobins (MbCN and metMb). Whereas the more distant tryptophan (Trp7) relaxes by energy transfer to the heme, Trp14 excitation predominantly decays by electron transfer to the heme. The excited Trp14→heme electron transfer occurs in <40 picoseconds with a quantum yield of more than 60%, over an edge-to-edge distance below ~10 angstroms, outcompeting the FRET process. Our results raise the question of whether such electron transfer pathways occur in a larger class of proteins.