The parallel helices of the intermediate filaments of alpha-keratin.

The research article discusses an investigation into the structure of alpha-keratin fibers in horse hair using infrared spectroscopy techniques. The study found that the alpha helices in the intermediate filaments of the fibers are parallel, contradicting previous claims of them being anti-parallel.

Methodology

• The researchers used Fourier transform infrared spectroscopy (FTIR) together with an attenuated total reflection technique (ATR). This technique allowed them to study the structure of alpha-keratin fibers in horse hair.
• The fibers were studied under two circumstances: when they were extended in water at 21 degrees Celsius and when they were extended in water at 95 degrees Celsius.
• In both cases, the fibers were extended to a strain of 40-50%.

Findings at 21 degrees Celsius

• The researchers observed that when the fibers were extended to 40-50% strain in water at 21 degrees Celsius, their alpha-helices completely disappeared. In their place, parallel beta-sheets were formed.

Findings at 95 degrees Celsius

• When the fibers were extended to the same strain at 95 degrees Celsius, however, the result was the formation of anti-parallel beta-sheets. This indicates that the relatively more stable anti-parallel beta-state is only attained in extended alpha-keratin fibers at elevated temperatures.
• The formation of these anti-parallel beta-sheets must result from a major molecular rearrangement within the fibers.

Conclusions

• Based on these results, it was concluded that the alpha-helices in the intermediate filaments (IFs) of alpha-keratin fibers must be parallel. This is in opposition to previous assertions that these alpha-helices are anti-parallel, a belief which was largely based on the findings of older studies that used X-ray diffraction to investigate the structure of beta-keratin in highly extended fibers.