Scientists trace gecko footprint, find clue to glue

Geckos' ability to scamper up walls with ease has long inspired scientists who study the fine keratin hairs on these creatures' footpads, believed responsible for the adhesion. Researchers at The University of Akron have discovered that geckos' ability to adhere to surfaces is not all about keratin. Clues lie in the lipids left behind in gecko footprints.

This discovery by researchers Ping Yuan Hsu and Liehui Ge, both UA polymer science graduate students; Alyssa Stark, UA integrated bioscience graduate student; Xiaopeng Li, chemistry research scientist; Chrys Wesdemiotis, distinguished professor ofchemistry; Peter Niewiarowski, interim director, UA Integrated Bioscience, Ph.D. Program; and Ali Dhinojwala, chair of the UA Department of Polymer Science, is published in Interface, the Journal of the Royal Society under the title: Direct evidence of phospholipids in gecko footprints and spatula–substrate contact interface detected using surface-sensitive spectroscopy.

The researchers' analysis of the near-invisible gecko footprints reveals the presence of phospholipids, according to Dhinojwala. This material, he says, has not been considered in current models of gecko adhesion and now provides the missing link in understanding superhydrophobicity, self-cleaning and fluid-like adhesion and release of gecko feet.

Dhinojwala, a pioneer in gecko-inspired adhesive research, says the lipids in gecko footprints have significant implications for scientists working to design synthetic adhesives that could be reused thousands of times over, such as for wall-climbing robots, microelectronics, adhesive tapes and bioadhesives.

More information: Direct evidence of phospholipids in gecko footprints and spatula–substrate contact interface detected using surface-sensitive spectroscopy, J. R. Soc. Interface, Published online before print August 24, 2011, doi: 10.1098/?rsif.2011.0370

Abstract
Observers ranging from Aristotle to young children have long marvelled at the ability of geckos to cling to walls and ceilings. Detailed studies have revealed that geckos are ‘sticky’ without the use of glue or suction devices. Instead, a gecko's stickiness derives from van der Waals interactions between proteinaceous hairs called setae and substrate. Here, we present surprising evidence that although geckos do not use glue, a residue is transferred on surfaces as they walk—geckos leave footprints. Using matrix-free nano-assisted laser desorption-ionization mass spectrometry, we identified the residue as phospholipids with phosphocholine head groups. Moreover, interface-sensitive sum-frequency generation spectroscopy revealed predominantly hydrophobic methyl and methylene groups and the complete absence of water at the contact interface between a gecko toe pad and the substrate. The presence of lipids has never been considered in current models of gecko adhesion. Our analysis of gecko footprints and the toe pad–substrate interface has significant consequences for models of gecko adhesion and by extension, the design of synthetic mimics.

Provided by University of Akron

Tail hair tells tale of cattle`s diet -- Scientists trace grassland production

 Tail hair can show if cattle have been grass-fed or not, according to scientists. By chemically analysing the tail hair, it is also possible for scientists to tell if, and when, a grass diet has been substituted for other types of feed over the past 12 months.

The findings published in the Journal of Agricultural and Food Chemistry show a clear scientific traceability and verification of grassland production.

“We can no longer depend on paperwork alone to trace production methods or feeds given to farm animals,” says Professor Frank Monahan from the UCD School of Agriculture, Food Science, and Veterinary Medicine at University College Dublin, and the UCD Institute of Food and Health, the first author of the scientific study.

“A tail hair of approximately 30 centimetres in length contains over a year’s information on the animal’s diet, with the hair closest to the skin holding clues to the most recent diet,” he explains.

“By plucking a hair from the tail, cutting it into millimetre segments, and analysing these in sequence we can get information about the diet over the previous days, weeks and months and, importantly, when the diet was changed,” explains Professor Monahan.

The method involves combusting the tail hair and measuring the isotopes of hydrogen, carbon, nitrogen and sulphur emitted.

Following the analysis, the scientists can almost identify the precise day when the grass diet of the animal may have been substituted with cereal or concentrate.

According to the scientists, omega 3 fatty acids are significantly higher in grass-fed beef than they are in cereal-fed beef.  As a result, beef from grass-fed cattle is often labelled and marketed on the basis of having high levels of omega 3 fatty acids and CLA (which together have been linked to several health benefits in humans).

“Consumers are increasingly interested in the origin and authenticity of the food they consume. So there is a clear need for reliable methods to verify the dietary history of farm animals,” says Dr. Aidan Moloney from the Animal and Grassland Research and Innovation Centre at Teagasc, the Irish Agriculture and Food Development Authority, who co-authored the study.

In the US food labels identifying if a farm animal has been ‘grass-fed’ allows for a premium to be charged for the product.

The scientists believe that a similar labelling could help the Irish beef industry to introduce a premium for its products.

The research was funded by the Irish Government’s Department of Agriculture, Fisheries and Food.

In 2006, US scientists used a similar method of chemically analysing tail hair to track the movement of elephants in Kenya. The aim was to help conservationists decide where to locate Elephant sanctuaries. The analysis showed that some elephants in the sanctuaries had raided nearby crop fields for food, a cause for concern among the local populations.

More information: 'Beef authentication and retrospective dietary verification using stable isotope ratio analysis of bovine muscle and tail hair.' Osorio, M.T, et al. (2011) Journal of Agricultural and Food Chemistry, 59 (7), pp 3295–3305

Provided by University College Dublin