Άλφα έλικα

 Το λήμμα δεν περιέχει πηγές ή αυτές που περιέχει δεν επαρκούν. Μπορείτε να βοηθήσετε προσθέτοντας την κατάλληλη τεκμηρίωση. Υλικό που είναι ατεκμηρίωτο μπορεί να αμφισβητηθεί και να αφαιρεθεί.
Η σήμανση τοποθετήθηκε στις 25/06/2015.
Η δομή της αιμοσφαιρίνης, αποτελούμενη κυρίως από άλφα-έλικες

Με την ονομασία άλφα έλικα (αγγλ. Alpha helix), ή έλικα άλφα, ή α-έλικα, (alpha helix, ή a-helix), φέρεται στη Βιολογία μια σπειροειδής αλυσίδα πολυπεπτιδίων η οποία και δημιουργεί μια ελικοειδή δομή σε πολλές πρωτεΐνες με 3,6 κατάλοιπα αμινοξέων ανά στροφή της έλικας. Οι διαδοχικές αυτές στροφές της άλφα έλικας συνδέονται με ασθενείς ενδομοριακούς δεσμούς υδρογόνου, με συνέπεια η δομή να είναι περισσότερο σταθερή από μια απλή, μη σπειροειδή αλυσίδα πολυπεπτιδίων.[1]

Στη διεθνή ορολογία, ονομάζεται και Pauling–Corey–Branson α-helix, λόγω της επιστημονικής συνεισφοράς των εν λόγω βιοχημικών - ερευνητών, το 1951, τόσο στην ανακάλυψη της δομής της όσο και στη σκιαγράφηση της λειτουργίας της.[2]

Η εν λόγω δομή της μακράς αλυσίδας "έλικας άλφα" είναι η χαρακτηριστική εκείνη που απαντάται στις "ινώδεις πρωτεΐνες" οι οποίες και βρίσκονται στα μαλλιά, στις τρίχες (τρίχωμα), στα πούπουλα, στα νύχια και στα κέρατα. Όλες οι πρωτεΐνες που βρίσκονται μεταξύ των κυττάρων είναι συνηθέστερα "σφαιρικού τύπου" με πολύ μικρά τμήματα ελίκων άλφα.

Παραπομπές

  1. ↑ J. M. Berg· J. L. Tymoczko· G. J. Gatto· L. Stryer (2015). Βιοχημεία. Πανεπιστημιακές Εκδόσεις Κρήτης. σελ. 41, 42. [νεκρός σύνδεσμος]
  2. ↑ «The structure of proteins; two hydrogen-bonded helical configurations of the polypeptide chain». Proceedings of the National Academy of Sciences of the United States of America 37 (4): 205–11. April 1951. doi:10.1073/pnas.37.4.205. PMID 14816373. Bibcode: 1951PNAS...37..205P. 

 

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