title: Protein clustering in chemically stressed HeLa cells studied by infrared nanospectroscopy.
abstract: Photo-Thermal Induced Resonance (PTIR) nanospectroscopy, tuned towards amide-I absorption, was used to study the distribution of proteic material in 34 different HeLa cells, of which 18 were chemically stressed by oxidative stress with Na3AsO3. The cell nucleus was found to provide a weaker amide-I signal than the surrounding cytoplasm, while the strongest PTIR signal comes from the perinuclear region. AFM topography shows that the cells exposed to oxidative stress undergo a volume reduction with respect to the control cells, through an accumulation of the proteic material around and above the nucleus. This is confirmed by the PTIR maps of the cytoplasm, where the pixels providing a high amide-I signal were identified with a space resolution of ∼300 × 300 nm. By analyzing their distribution with two different statistical procedures we found that the probability to find protein clusters smaller than 0.6 μm in the cytoplasm of stressed HeLa cells is higher by 35% than in the control cells. These results indicate that it is possible to study proteic clustering within single cells by label-free optical nanospectroscopy.
authors.affiliation: Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, V.le Regina Elena 291, 00161 Roma, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Giliberti
authors.affiliation: Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, V.le Regina Elena 291, 00161 Roma, Italy and Dipartimento di Fisica, Università di Roma La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy. paolo.calvani@roma1.infn.it.
authors.forename: L
authors.initials: L
authors.lastname: Baldassarre
authors.affiliation: Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, V.le Regina Elena 291, 00161 Roma, Italy and Dipartimento di Biologia e Biotecnologie Charles Darwin, Universita di Roma La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Rosa
authors.affiliation: Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, V.le Regina Elena 291, 00161 Roma, Italy.
authors.forename: V
authors.initials: V
authors.lastname: de Turris
authors.affiliation: Dipartimento di Fisica, Università di Roma La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy. paolo.calvani@roma1.infn.it.
authors.forename: M
authors.initials: M
authors.lastname: Ortolani
authors.affiliation: Dipartimento di Fisica, Università di Roma La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy. paolo.calvani@roma1.infn.it.
authors.forename: P
authors.initials: P
authors.lastname: Calvani
authors.affiliation: Dipartimento di Fisica, Università di Roma La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy. paolo.calvani@roma1.infn.it.
authors.forename: A
authors.initials: A
authors.lastname: Nucara
mesh_terms: D002467:Cell Nucleus / Q000737:chemistry*; D003593:Cytoplasm / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D036103:Nanotechnology; D011506:Proteins / Q000032:analysis*; D013055:Spectrophotometry, Infrared
chemical_list: D011506:Proteins