Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Heads up, tails down

27.09.2010
Advanced laser spectroscopy exposes the unique organization of water molecules under model membrane surfaces

The behavior of water molecules as they contact biological substances has long puzzled scientists.

The first few layers of interfacial water can display complex arrangements that distinctly influence biochemical reactivity and function. Mapping these interfaces, however, is extremely difficult because chemical signatures of surface-bound water are often swamped by bulk liquid signals. Now, researchers led by Tahei Tahara from the RIKEN Advanced Science Institute in Wako have developed a laser spectroscopy technique that conclusively determines the orientation of water molecules beneath charged lipid layers—the primary components of cell membranes1.

Phospholipids are fatty acid molecules that contain two parts: hydrophobic ‘tails’ made of long hydrocarbon chains and hydrophilic ‘heads’ comprised of charged phosphate groups and other organic units. At the air–water interface, phospholipids spontaneously form into monolayer films, with their tails extending into the air and their heads immersed in water. The structure and orientation of water molecules below such monolayers has been a matter of controversy. Some investigators suggest that the partially positive-charged hydrogen atoms of water orientate ‘up’ or ‘down’ to align with the lipid head charge, while others suggest the opposite outcome.

Tahara and colleagues resolved this debate by using an optical technique called heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy, which has extremely high surface sensitivity. HD-VSFG combines two laser beams with different frequencies at an interface to generate a sum-frequency signal; when vibrations of surface molecules resonate with the applied laser, the sum-frequency signal rapidly shoots up—instantly identifying which chemicals are present. Because this signal originates from non-linear surface polarization effects, it contains only contributions from interfacial species. “HD-VSFG automatically probes the depths of water layers that are different from the bulk,” says Tahara.

Determining the orientation of surface water required heterodyne detection, a method that determines the phase of weak signals via interference with a reference beam. According to Tahara, performing such measurements required precisely sensing changes to the signal light’s optical phase—meaning the researchers had to control the laser beams with nanometer-scale accuracy.

The teams’ experiments on three different lipid monolayers revealed that the interfacial structures are governed by the net charge of the heads: water hydrogen atoms pointed up with anionic lipid heads, and faced downwards in the presence of cationic lipids. “This is totally different from the situation for reactions in aqueous solutions,” says Tahara, who believes that the results will shed light on important reactions that take place at cell membranes, such as enzyme activation.

The corresponding author for this highlight is based at the Molecular Spectroscopy Laboratory, RIKEN Advanced Science Institute

Journal information
1. Mondal, J.A., Nihonyanagi, S., Yamaguchi, S. & Tahara, T. Structure and orientation of water at charge lipid monolayer/water interfaces probed by heterodyne-detected vibrational sum frequency generation spectroscopy. Journal of the American Chemical Society 132, 10656–10657 (2010).

gro-pr | Research asia research news
Further information:
http://www.rikenresearch.riken.jp/eng/research/6394
http://www.researchsea.com

More articles from Life Sciences:

nachricht Newly designed molecule binds nitrogen
23.02.2018 | Julius-Maximilians-Universität Würzburg

nachricht Atomic Design by Water
23.02.2018 | Max-Planck-Institut für Eisenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>