We analyse research collaborations as measured by co-publications in the field of non-pharmaceutical diabetes 2, for Europe as a whole and for individual countries separately. We are interested in the determinants of research collaboration. We explain the interaction intensity between any two research organizations by their proximity in five dimensions: cognitive, organizational, social, institutional, and geographical. Statistical analysis on the pan-European collaboration network shows social proximity is the most important determinant of collaboration, where social proximity refers to the extent two organizations have collaborated in the past. Repeating the analysis for individual European countries, we show that the determinants of research collaboration differ widely among countries. In particular, we find that institutional proximity, indicating the extent to partners come from the same institutional sphere (university, hospital, industry, government) plays a significant role only in Italy, Greece, Spain and Switzerland, which indicates that in these countries triple helix nteractions (including public-private partnerships) are less well eveloped than in other European countries