Unravelling the nanostructure of strawberry fruit pectins by endo-polygalacturonase digestion and atomic force microscopy.
Pectins analysed by AFM are visualized as individual chains, branched or unbranched, and aggregates. To investigate the nature of these structures, sodium carbonate soluble pectins from strawberry fruits were digested with endo-polygalacturonase M2 from Aspergillus aculeatus and visualized by AFM. A gradual decrease in the length of chains was observed as result of the treatment, reaching a minimum LNvalue of 22nm. The branches were not visible after 2h of enzymatic incubation. The size of complexes also diminished significantly with the enzymatic digestion. A treatment to hydrolyse rhamnogalacturonan II borate diester bonds neither affected chains length or branching nor complex size but reduced the density of aggregates. These results suggest that chains are formed by a mixture of homogalacturonan and more complex molecules composed by a homogalacturonan unit linked to an endo-PG resistant unit. Homogalacturonan is a structural component of the complexes and rhamnogalacturonan II could be involved in their formation.
Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora" (IHSM-UMA-CSIC), Departamento de Biología Vegetal, Universidad de Málaga, 29071 Málaga, Spain.
Candelas
C
Paniagua
Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK.
Andrew R
AR
Kirby
Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK.
A Patrick
AP
Gunning
Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK.
Victor J
VJ
Morris
Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora" (IHSM-UMA-CSIC), Departamento de Biología Vegetal, Universidad de Málaga, 29071 Málaga, Spain.
Antonio J
AJ
Matas
Departamento de Biología Vegetal, Universidad de Málaga, 29071 Málaga, Spain.
Miguel A
MA
Quesada
Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora" (IHSM-UMA-CSIC), Departamento de Biología Vegetal, Universidad de Málaga, 29071 Málaga, Spain. Electronic address: mercado@uma.es.
José A
JA
Mercado
D031985:Fragaria; D005638:Fruit / Q000737:chemistry*; D006603:Hexuronic Acids / Q000032:analysis; D006868:Hydrolysis; D018625:Microscopy, Atomic Force / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry*; D010368:Pectins / Q000737:chemistry* / Q000378:metabolism; D011096:Polygalacturonase / Q000378:metabolism*
D006603:Hexuronic Acids; C042492:rhamnogalacturonan II; C007819:galacturonic acid; D010368:Pectins; D011096:Polygalacturonase
Atomic force microscopy; Cell wall; Fragaria×ananassa; Homogalacturonan; Pectins; Rhamnogalacturonan; Strawberry