Alcohol content of red wine has an impact on mouth-feel and now researchers are closer to understanding why. Lower alcohol wines are perceived as more puckering than higher alcohol wines even when they have the same amount of tannin. New research has shown that this may be because alcohol can prevent wine tannins from binding strongly to saliva proteins.
 
Astringency mostly involves wine tannins binding to proteins in saliva. Wine tannins are complex molecules that have both hydrophilic (water-loving) and hydrophobic (water-fearing) parts, both of which can stick to proteins. 
 
The recent study, which was conducted with the University of Queensland, showed that tannins in lower alcohol (10%) model wines grip more tightly to salivary proteins than those in higher alcohol (15%) model wines
 
In higher alcohol wines the alcohol can prevent the hydrophobic parts of the tannin from sticking to proteins, leaving only the hydrophilic parts to do the heavy lifting. In low alcohol wines, both parts of the tannins can stick to proteins, enabling the tannins to bind more tightly. This may be something to consider when producing lower alcohol wines.
REFERENCE

McRae, J.M.; Ziora, Z.M.; Kassara, S.; Cooper, M.A.; Smith, P.A. Ethanol concentration influences the mechanisms of wine tannin interactions with poly(L-proline) in model wine. J. Agric. Food Chem. 2015, doi: 10.1021/acs.jafc.5b00758