Giorgio Giacometti | Università degli Studi di Padova (original) (raw)
Papers by Giorgio Giacometti
IOS Press , Ohmsha eBooks, 2001
... ed Arti); the Italian Society of Pure and Applied Biophysics SIB PA (Societa Italiana di Biof... more ... ed Arti); the Italian Society of Pure and Applied Biophysics SIB PA (Societa Italiana di Biofisica Pura ed Applicata); and ... Applications to Photosynthesis, D. Carbonera 105 Electron Spin Echo Envelope Modulation Spectroscopy in the Study of Biological Systems, L. Bubacco 123 ...
![Research paper thumbnail of Crystal structure of the [FeFe]-hydrogenase maturation protein HydF](https://attachments.academia-assets.com/118487631/thumbnails/1.jpg)
](with specic help available everywhere you see the i O symbol. The following versions of software ... more with specic help available everywhere you see the i O symbol. The following versions of software and data (see references i O) were used in the production of this report:
European journal of biochemistry, Dec 1, 1995
Photosystem I and II core complexes were resolved in a single step from the thylakoid membrane of... more Photosystem I and II core complexes were resolved in a single step from the thylakoid membrane of Synechocystis sp. PCC 6803 by using a mild solubilization procedure in dodecyl beta-D-maltoside and Deriphat/PAGE. For each photosystem, two green bands were obtained containing oligomeric and monomeric forms of the core complexes of either photosystem. The oligomers are likely to be trimers in the case of photosystem I and dimers for photosystem II. The absorption spectra, polypeptide and pigment composition of green bands corresponding to either photosystem I or photosystem II were identical for monomeric and oligomeric forms. The cytochrome b-559 content of photosystem II was evaluated to be one cytochrome b-559/reaction centre both in the monomeric and dimeric forms. Two new 15-kDa and 22-kDa carotenoid-binding protein were isolated and their polypeptides purified to homogeneity.
FEBS Letters, Aug 15, 2005
Seven genes seem to encode for putative ClC chloride channels (AtClC-a to AtClC-g) in Arabidopsis... more Seven genes seem to encode for putative ClC chloride channels (AtClC-a to AtClC-g) in Arabidopsis thaliana. Their function and localization is still largely unknown. AtClC-f shares considerable sequence similarity with putative ClC channel proteins from Synechocystis, considered to represent the precursor of chloroplasts. We show by biochemical and mass spectrometry analysis that ClC-f is located in the outer envelope membrane of spinach chloroplasts. Consistent with the plastidial localization of ClC-f, p-chlorophenoxy-acetic acid (CPA) reduces photosynthetic activity and the protein is expressed in etioplasts and chloroplasts but not in root tissue. These findings may represent a step toward the molecular identification of ion channel activities in chloroplast membranes.
Photosynthesis Research, Jun 1, 2006
This paper tells the history of two brothers, almost a generation apart in age, who met again, af... more This paper tells the history of two brothers, almost a generation apart in age, who met again, after having followed different academic paths, to introduce biophysical research in photosynthesis at the University of Padova. The development of two research groups, one in the Chemistry Department, the other in the Biology Department led to a comprehensive interdisciplinary group across academic barriers. The group of Giovanni Giacometti developed in Physical Chemistry, during the years before his retirement, with some roots which can be traced to the famous Linus Pauling school of the mid 1950s, and made possible, by the work of many students (especially Donatella Carbonera and Marilena Di Valentin) and of an older associate (Giancarlo Agostini). The group participated quite actively with a number of European and American laboratories in the application of physical techniques, especially Electron Spin Resonance (EPR) associated with Optical Spectroscopy (Optically Detected Magnetic Resonance; ODMR), and contributed to the development of the understanding of the structure-function relationships in photosynthetic membrane complexes, stimulated by the determination
FEBS Letters, Oct 12, 1992
When isolated photosystem I1 reaction centers from spinach are exposed to photoinhibitory light i... more When isolated photosystem I1 reaction centers from spinach are exposed to photoinhibitory light in the presence of an electron aceeptor, breakdown products of the D2 protein at 28, 25, 23, 18, 9, 5 and 4.5 kDa are detected by immunoblotting with a monospeeifie anti-D2 polyelonal antibody. In a time-course experi~i~ent the 23 and 4.5 kDa fragments show a transient appearance, whilst the others are photoaceumulated. The regions of the D2 protein containing tl~e cleavage sites tbr the 28 and 18 kDa photoindueed fragments have been identified. Significant degradation of D2 takes place only in the presence: of an electron aeceptor, and breakdown of the protein is partially prevented by serine-type proteas¢ inhibitors.
Applied Magnetic Resonance, Nov 10, 2009
The origin of life as is presently known on our planet is deeply connected with the evolution of ... more The origin of life as is presently known on our planet is deeply connected with the evolution of photosynthesis as a mean of providing the chemical substances necessary for the energy requirements of all the complex functions of living organisms. Light energy from the sun radiation is the only and primary source for this energetic endeavor. The evolution of the photosynthetic machinery is a complex biological issue, with links to the more general issue of the early planetary changes following the massive appearance of dioxygen in the atmosphere. Evidences, on which a possible story of this development can be based, have emerged from micro-paleontology and have given rise to some speculation and hypotheses. But a much stronger drive toward an understanding of the problem is connected with the copious results which modern molecular biology and biophysics are currently producing with the advent of molecular phylogenetic techniques and with the knowledge of the detailed atomic structure of the giant molecules that nature has developed to perform otherwise impossible chemical tasks. This minireview gives some of the basic facts and some of the discussion for an approach to the story.
Biochemical and Biophysical Research Communications, Aug 1, 2000
The Arabidopsis thaliana potassium channel KAT1 was expressed and characterized in Chinese hamste... more The Arabidopsis thaliana potassium channel KAT1 was expressed and characterized in Chinese hamster ovary cells. KAT1-GFP fusion protein was successfully targeted to the plasma membrane and electrophysiological analysis revealed functional expression of KAT1 only in cells cultured at 30°C. The main biophysical characteristics of KAT1 are similar to those described for the channel expressed in other systems. CHO cells represent an advantageous expression system and may be the system of choice to study the expression, assembly, function, and regulation of plant potassium channels in general.
Biochemical Journal, Nov 1, 1978
Biochimica Et Biophysica Acta - Bioenergetics, Mar 1, 2011
Bioinformatic approaches have allowed the identification in Arabidopsis thaliana of twenty genes ... more Bioinformatic approaches have allowed the identification in Arabidopsis thaliana of twenty genes encoding for homologues of animal ionotropic glutamate receptors (iGLRs). Some of these putative receptor proteins, grouped into three subfamilies, have been located to the plasmamembrane, but their possible location in organelles has not been investigated so far. In the present work we provide multiple evidence for the plastid localization of a glutamate receptor, AtGLR3.4, in Arabidopsis and tobacco. Biochemical analysis was performed using an antibody shown to specifically recognize both the native protein in Arabidopsis and the recombinant AtGLR3.4 fused to YFP expressed in tobacco. Western blots indicate the presence of AtGLR3.4 in both the plasmamembrane and in chloroplasts. In agreement, in transformed Arabidopsis cultured cells as well as in agroinfiltrated tobacco leaves, AtGLR3.4::YFP is detected both at the plasmamembrane and at the plastid level by confocal microscopy. The photosynthetic phenotype of mutant plants lacking AtGLR3.4 was also investigated. These results identify for the first time a dual localization of a glutamate receptor, revealing its presence in plastids and chloroplasts and opening the way to functional studies.
FEBS Letters, Feb 15, 1976
BMC Plant Biology, Jun 9, 2009
Background: Photosystems are composed of two moieties, a reaction center and a peripheral antenna... more Background: Photosystems are composed of two moieties, a reaction center and a peripheral antenna system. In photosynthetic eukaryotes the latter system is composed of proteins belonging to Lhc family. An increasing set of evidences demonstrated how these polypeptides play a relevant physiological function in both light harvesting and photoprotection. Despite the sequence similarity between antenna proteins associated with the two Photosystems, present knowledge on their physiological role is mostly limited to complexes associated to Photosystem II. Results: In this work we analyzed the physiological role of Photosystem I antenna system in Arabidopsis thaliana both in vivo and in vitro. Plants depleted in individual antenna polypeptides showed a reduced capacity for photoprotection and an increased production of reactive oxygen species upon high light exposure. In vitro experiments on isolated complexes confirmed that depletion of antenna proteins reduced the resistance of isolated Photosystem I particles to high light and that the antenna is effective in photoprotection only upon the interaction with the core complex. Conclusion: We show that antenna proteins play a dual role in Arabidopsis thaliana Photosystem I photoprotection: first, a Photosystem I with an intact antenna system is more resistant to high light because of a reduced production of reactive oxygen species and, second, antenna chlorophyllproteins are the first target of high light damages. When photoprotection mechanisms become insufficient, the antenna chlorophyll proteins act as fuses: LHCI chlorophylls are degraded while the reaction center photochemical activity is maintained. Differences with respect to photoprotection strategy in Photosystem II, where the reaction center is the first target of photoinhibition, are discussed.
Zeitschrift für Naturforschung C, 2000
The interaction between azurin from Pseudomonas aeruginosa and Ag(I), Cu(II), Hg(II), was investi... more The interaction between azurin from Pseudomonas aeruginosa and Ag(I), Cu(II), Hg(II), was investigated as a function of protein state, i.e. apo-, reduced and oxidised azurin. Two different metal binding sites, characterized by two different spectroscopic absorbancies, were detected: one is accessible to Ag(I) and Cu(II) but not to Hg(II); the other one binds Ag(I) and Hg(II) but not copper. When added in stoichiometric amount, Ag(I) shows high affinity for the redox center of apo-azurin, to which it probably binds by the -SH group of Cys112; it can displace Cu(I) from reducedazurin, while it does not bind to the redox center of oxidizedazurin. Kinetic experiments show that Ag(I) binding to the reducedform is four times faster than binding to the apo-form. This result suggests that metal binding requires a conformational rearrangement of the active site of the azurin. Interaction of A g(I) or Hg(II) ions to the second metal binding site, induces typical changes of UV spectrum and que...
Archives of Biochemistry and Biophysics, 1988
Octopus vulgaris hemocyanin in 11 S aggregation state binds oxygen following a noncooperative oxy... more Octopus vulgaris hemocyanin in 11 S aggregation state binds oxygen following a noncooperative oxygen saturation curve with Hill coefficient n = 1. Under the same conditions the equilibrium and kinetics of the reaction with cyanide and other ligands are indicative of an anticooperative behavior displaying different characteristics for the different ligands. The data are consistent with an induced-fit type allosteric model which assumes for the 11 S subunit of 0. vulgaris hemocyanin an annular structure made up by five identical domains each containing one binding site whose reactivity is near-neighbor regulated.
Cellular Physiology and Biochemistry, 2010
Cell Swelling-induced Insulin Secretion from INS-1E Cells is Inhibited by Extracellular Ca 2+ and... more Cell Swelling-induced Insulin Secretion from INS-1E Cells is Inhibited by Extracellular Ca 2+ and is Tetanus Toxin Resistant
Molecular Crystals and Liquid Crystals, 1986
Page 1. Md. Crysf. Liq. Cryst., 1986, Vol. 141, pp, 165-178 0026-8941 18611412-0165/$20.00/ 0 0 1... more Page 1. Md. Crysf. Liq. Cryst., 1986, Vol. 141, pp, 165-178 0026-8941 18611412-0165/$20.00/ 0 0 1986 Gordon and Breach Science Publishers SA Printed in the United States of America Crystal Structure of the 1:l CT Complex of Biphenylene with ...
Theoretica Chimica Acta, 1963
An improvement of the McConnell formula for the correlation of hydrogen coupling constants in alt... more An improvement of the McConnell formula for the correlation of hydrogen coupling constants in alternant hydrocarbon ions is derived. The new formula is analogous to the one recently proposed by COL~A and BOLTON and is obtained without introducing any charge effect but only considering, in the first order perturbation expansion, terms arising from hydrogen next nearest neighbour carbon p orbitals. Die McConnell-Formel fiir die Wasserstoff-Kopphngskonstante in alternierenden Kohlenwasserstoffionen wird verbessert. Die neue Formel ist ein Analogon der kiirzlich yon Cor,I,A und Bor.To~ vorgeschlagenen, wird aber ohne Einfiihrung yon Ladungseffekten erhalten. Sic ergibt sich vielmchr durch Hinzunahme der Glicder, die die der CH-Bindung benaehbarten Kohlenstoff-p-Eigenfunktionen in erster N~therung beriicksichtigen. La formule de 3s pour les constantes de couplage hypcrfin protonique dans les ions des hydrocarbures alternants est am61ior6e. La nouvclle formule est analogue & une autre propos~e r@cemment par CoL~A et BOLTON; on l'obtient, sans introduire des effets de charge, seulement par inclusion des termes perturbateurs de premier ordre, d@rivant des orbitales p des carbones adjacent s la liaison C-H eonsid~r6e.
IOS Press , Ohmsha eBooks, 2001
... ed Arti); the Italian Society of Pure and Applied Biophysics SIB PA (Societa Italiana di Biof... more ... ed Arti); the Italian Society of Pure and Applied Biophysics SIB PA (Societa Italiana di Biofisica Pura ed Applicata); and ... Applications to Photosynthesis, D. Carbonera 105 Electron Spin Echo Envelope Modulation Spectroscopy in the Study of Biological Systems, L. Bubacco 123 ...
with specic help available everywhere you see the i O symbol. The following versions of software ... more with specic help available everywhere you see the i O symbol. The following versions of software and data (see references i O) were used in the production of this report:
European journal of biochemistry, Dec 1, 1995
Photosystem I and II core complexes were resolved in a single step from the thylakoid membrane of... more Photosystem I and II core complexes were resolved in a single step from the thylakoid membrane of Synechocystis sp. PCC 6803 by using a mild solubilization procedure in dodecyl beta-D-maltoside and Deriphat/PAGE. For each photosystem, two green bands were obtained containing oligomeric and monomeric forms of the core complexes of either photosystem. The oligomers are likely to be trimers in the case of photosystem I and dimers for photosystem II. The absorption spectra, polypeptide and pigment composition of green bands corresponding to either photosystem I or photosystem II were identical for monomeric and oligomeric forms. The cytochrome b-559 content of photosystem II was evaluated to be one cytochrome b-559/reaction centre both in the monomeric and dimeric forms. Two new 15-kDa and 22-kDa carotenoid-binding protein were isolated and their polypeptides purified to homogeneity.
FEBS Letters, Aug 15, 2005
Seven genes seem to encode for putative ClC chloride channels (AtClC-a to AtClC-g) in Arabidopsis... more Seven genes seem to encode for putative ClC chloride channels (AtClC-a to AtClC-g) in Arabidopsis thaliana. Their function and localization is still largely unknown. AtClC-f shares considerable sequence similarity with putative ClC channel proteins from Synechocystis, considered to represent the precursor of chloroplasts. We show by biochemical and mass spectrometry analysis that ClC-f is located in the outer envelope membrane of spinach chloroplasts. Consistent with the plastidial localization of ClC-f, p-chlorophenoxy-acetic acid (CPA) reduces photosynthetic activity and the protein is expressed in etioplasts and chloroplasts but not in root tissue. These findings may represent a step toward the molecular identification of ion channel activities in chloroplast membranes.
Photosynthesis Research, Jun 1, 2006
This paper tells the history of two brothers, almost a generation apart in age, who met again, af... more This paper tells the history of two brothers, almost a generation apart in age, who met again, after having followed different academic paths, to introduce biophysical research in photosynthesis at the University of Padova. The development of two research groups, one in the Chemistry Department, the other in the Biology Department led to a comprehensive interdisciplinary group across academic barriers. The group of Giovanni Giacometti developed in Physical Chemistry, during the years before his retirement, with some roots which can be traced to the famous Linus Pauling school of the mid 1950s, and made possible, by the work of many students (especially Donatella Carbonera and Marilena Di Valentin) and of an older associate (Giancarlo Agostini). The group participated quite actively with a number of European and American laboratories in the application of physical techniques, especially Electron Spin Resonance (EPR) associated with Optical Spectroscopy (Optically Detected Magnetic Resonance; ODMR), and contributed to the development of the understanding of the structure-function relationships in photosynthetic membrane complexes, stimulated by the determination
FEBS Letters, Oct 12, 1992
When isolated photosystem I1 reaction centers from spinach are exposed to photoinhibitory light i... more When isolated photosystem I1 reaction centers from spinach are exposed to photoinhibitory light in the presence of an electron aceeptor, breakdown products of the D2 protein at 28, 25, 23, 18, 9, 5 and 4.5 kDa are detected by immunoblotting with a monospeeifie anti-D2 polyelonal antibody. In a time-course experi~i~ent the 23 and 4.5 kDa fragments show a transient appearance, whilst the others are photoaceumulated. The regions of the D2 protein containing tl~e cleavage sites tbr the 28 and 18 kDa photoindueed fragments have been identified. Significant degradation of D2 takes place only in the presence: of an electron aeceptor, and breakdown of the protein is partially prevented by serine-type proteas¢ inhibitors.
Applied Magnetic Resonance, Nov 10, 2009
The origin of life as is presently known on our planet is deeply connected with the evolution of ... more The origin of life as is presently known on our planet is deeply connected with the evolution of photosynthesis as a mean of providing the chemical substances necessary for the energy requirements of all the complex functions of living organisms. Light energy from the sun radiation is the only and primary source for this energetic endeavor. The evolution of the photosynthetic machinery is a complex biological issue, with links to the more general issue of the early planetary changes following the massive appearance of dioxygen in the atmosphere. Evidences, on which a possible story of this development can be based, have emerged from micro-paleontology and have given rise to some speculation and hypotheses. But a much stronger drive toward an understanding of the problem is connected with the copious results which modern molecular biology and biophysics are currently producing with the advent of molecular phylogenetic techniques and with the knowledge of the detailed atomic structure of the giant molecules that nature has developed to perform otherwise impossible chemical tasks. This minireview gives some of the basic facts and some of the discussion for an approach to the story.
Biochemical and Biophysical Research Communications, Aug 1, 2000
The Arabidopsis thaliana potassium channel KAT1 was expressed and characterized in Chinese hamste... more The Arabidopsis thaliana potassium channel KAT1 was expressed and characterized in Chinese hamster ovary cells. KAT1-GFP fusion protein was successfully targeted to the plasma membrane and electrophysiological analysis revealed functional expression of KAT1 only in cells cultured at 30°C. The main biophysical characteristics of KAT1 are similar to those described for the channel expressed in other systems. CHO cells represent an advantageous expression system and may be the system of choice to study the expression, assembly, function, and regulation of plant potassium channels in general.
Biochemical Journal, Nov 1, 1978
Biochimica Et Biophysica Acta - Bioenergetics, Mar 1, 2011
Bioinformatic approaches have allowed the identification in Arabidopsis thaliana of twenty genes ... more Bioinformatic approaches have allowed the identification in Arabidopsis thaliana of twenty genes encoding for homologues of animal ionotropic glutamate receptors (iGLRs). Some of these putative receptor proteins, grouped into three subfamilies, have been located to the plasmamembrane, but their possible location in organelles has not been investigated so far. In the present work we provide multiple evidence for the plastid localization of a glutamate receptor, AtGLR3.4, in Arabidopsis and tobacco. Biochemical analysis was performed using an antibody shown to specifically recognize both the native protein in Arabidopsis and the recombinant AtGLR3.4 fused to YFP expressed in tobacco. Western blots indicate the presence of AtGLR3.4 in both the plasmamembrane and in chloroplasts. In agreement, in transformed Arabidopsis cultured cells as well as in agroinfiltrated tobacco leaves, AtGLR3.4::YFP is detected both at the plasmamembrane and at the plastid level by confocal microscopy. The photosynthetic phenotype of mutant plants lacking AtGLR3.4 was also investigated. These results identify for the first time a dual localization of a glutamate receptor, revealing its presence in plastids and chloroplasts and opening the way to functional studies.
FEBS Letters, Feb 15, 1976
BMC Plant Biology, Jun 9, 2009
Background: Photosystems are composed of two moieties, a reaction center and a peripheral antenna... more Background: Photosystems are composed of two moieties, a reaction center and a peripheral antenna system. In photosynthetic eukaryotes the latter system is composed of proteins belonging to Lhc family. An increasing set of evidences demonstrated how these polypeptides play a relevant physiological function in both light harvesting and photoprotection. Despite the sequence similarity between antenna proteins associated with the two Photosystems, present knowledge on their physiological role is mostly limited to complexes associated to Photosystem II. Results: In this work we analyzed the physiological role of Photosystem I antenna system in Arabidopsis thaliana both in vivo and in vitro. Plants depleted in individual antenna polypeptides showed a reduced capacity for photoprotection and an increased production of reactive oxygen species upon high light exposure. In vitro experiments on isolated complexes confirmed that depletion of antenna proteins reduced the resistance of isolated Photosystem I particles to high light and that the antenna is effective in photoprotection only upon the interaction with the core complex. Conclusion: We show that antenna proteins play a dual role in Arabidopsis thaliana Photosystem I photoprotection: first, a Photosystem I with an intact antenna system is more resistant to high light because of a reduced production of reactive oxygen species and, second, antenna chlorophyllproteins are the first target of high light damages. When photoprotection mechanisms become insufficient, the antenna chlorophyll proteins act as fuses: LHCI chlorophylls are degraded while the reaction center photochemical activity is maintained. Differences with respect to photoprotection strategy in Photosystem II, where the reaction center is the first target of photoinhibition, are discussed.
Zeitschrift für Naturforschung C, 2000
The interaction between azurin from Pseudomonas aeruginosa and Ag(I), Cu(II), Hg(II), was investi... more The interaction between azurin from Pseudomonas aeruginosa and Ag(I), Cu(II), Hg(II), was investigated as a function of protein state, i.e. apo-, reduced and oxidised azurin. Two different metal binding sites, characterized by two different spectroscopic absorbancies, were detected: one is accessible to Ag(I) and Cu(II) but not to Hg(II); the other one binds Ag(I) and Hg(II) but not copper. When added in stoichiometric amount, Ag(I) shows high affinity for the redox center of apo-azurin, to which it probably binds by the -SH group of Cys112; it can displace Cu(I) from reducedazurin, while it does not bind to the redox center of oxidizedazurin. Kinetic experiments show that Ag(I) binding to the reducedform is four times faster than binding to the apo-form. This result suggests that metal binding requires a conformational rearrangement of the active site of the azurin. Interaction of A g(I) or Hg(II) ions to the second metal binding site, induces typical changes of UV spectrum and que...
Archives of Biochemistry and Biophysics, 1988
Octopus vulgaris hemocyanin in 11 S aggregation state binds oxygen following a noncooperative oxy... more Octopus vulgaris hemocyanin in 11 S aggregation state binds oxygen following a noncooperative oxygen saturation curve with Hill coefficient n = 1. Under the same conditions the equilibrium and kinetics of the reaction with cyanide and other ligands are indicative of an anticooperative behavior displaying different characteristics for the different ligands. The data are consistent with an induced-fit type allosteric model which assumes for the 11 S subunit of 0. vulgaris hemocyanin an annular structure made up by five identical domains each containing one binding site whose reactivity is near-neighbor regulated.
Cellular Physiology and Biochemistry, 2010
Cell Swelling-induced Insulin Secretion from INS-1E Cells is Inhibited by Extracellular Ca 2+ and... more Cell Swelling-induced Insulin Secretion from INS-1E Cells is Inhibited by Extracellular Ca 2+ and is Tetanus Toxin Resistant
Molecular Crystals and Liquid Crystals, 1986
Page 1. Md. Crysf. Liq. Cryst., 1986, Vol. 141, pp, 165-178 0026-8941 18611412-0165/$20.00/ 0 0 1... more Page 1. Md. Crysf. Liq. Cryst., 1986, Vol. 141, pp, 165-178 0026-8941 18611412-0165/$20.00/ 0 0 1986 Gordon and Breach Science Publishers SA Printed in the United States of America Crystal Structure of the 1:l CT Complex of Biphenylene with ...
Theoretica Chimica Acta, 1963
An improvement of the McConnell formula for the correlation of hydrogen coupling constants in alt... more An improvement of the McConnell formula for the correlation of hydrogen coupling constants in alternant hydrocarbon ions is derived. The new formula is analogous to the one recently proposed by COL~A and BOLTON and is obtained without introducing any charge effect but only considering, in the first order perturbation expansion, terms arising from hydrogen next nearest neighbour carbon p orbitals. Die McConnell-Formel fiir die Wasserstoff-Kopphngskonstante in alternierenden Kohlenwasserstoffionen wird verbessert. Die neue Formel ist ein Analogon der kiirzlich yon Cor,I,A und Bor.To~ vorgeschlagenen, wird aber ohne Einfiihrung yon Ladungseffekten erhalten. Sic ergibt sich vielmchr durch Hinzunahme der Glicder, die die der CH-Bindung benaehbarten Kohlenstoff-p-Eigenfunktionen in erster N~therung beriicksichtigen. La formule de 3s pour les constantes de couplage hypcrfin protonique dans les ions des hydrocarbures alternants est am61ior6e. La nouvclle formule est analogue & une autre propos~e r@cemment par CoL~A et BOLTON; on l'obtient, sans introduire des effets de charge, seulement par inclusion des termes perturbateurs de premier ordre, d@rivant des orbitales p des carbones adjacent s la liaison C-H eonsid~r6e.