Gas Chromatography-Mass Spectrometry Analysis of Agarwood Extracts from Mature and Juvenile Aquilaria malaccensis

International audienceChemical composition of crude extracts from infected woods of Aquilaria malaccensis were compared to that of healthy wood and commercial agarwood. Infected woods were collected six months after drilling of wild mature trees or after fungal inoculation into the stem of 4-year-old trees. Agarwood substances were extracted in methanol and were subjected to GC-MS analyses. The major compounds were chromone derivative, aromatic compounds, sesquiterpenes, monoterpenes, sterols and fatty acid methyl ester. Aromatic compounds constituted of aldehyde, phenol, ether and ketone groups. In the agarwood extract of the juvenile fungal-elicited tree but not in the healthy wood, some major compounds found were 2-(2-phenylethyl) chromone derivative, 4-phenyl-2-butanone, (1S, 4S, 7R)-1,4-dimethyl-7-(prop-1-en-2-yl)-1,2,3,4,5,6,7,8-octahydroazulene [guaiene], 1,1,4,7-tetramethyl-2,3,4,5,6,7,7a, 7b-octahydro-1aH-cyclopropa[h]azulen-4a-ol [palustrol], and 4-(4-methoxyphenyl) butan-2-one [anisylacetone]. These were also found from agarwood of different grades and agarwood collected from the wild mature tree, in addition to agarospirol, alloaromadendre oxide (2), alpha-elemol, gamma-eudesmol, and guaiol. This work demonstrated that in young A. malaccensis trees, fungi may be associated to the formation of important agarwood compounds and can be detected as early as six months after inoculation

Study of Arabidopsis thaliana BolA2 : Structure, Dynamics and Interaction with Glutaredoxins

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Letter to the Editor: 1H, 13C and 15N NMR assignment of the homodimeric poplar phloem type II peroxiredoxin

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Probing the Structure−Function Relationship of Polyene Macrolides: Engineered Biosynthesis of Soluble Nystatin Analogues

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Magnetic Susceptibility Tensor and Heme Contact Shifts Determinations in the Rhodobacter capsulatus Ferricytochrome c': NMR and Magnetic Susceptibility Studies

The [1]H and [15]N resonances of the carbon monoxide complex of ferrocytochrome c' of Rhodobacter capsulatus, a ferrous diamagnetic heme protein, have been extensively assigned by TOCSY−HSQC, NOESY−HSQC, and HSQC−NOESY−HSQC 3D heteronuclear experiments performed on a 7 mM sample labeled with [15]N. Based on short-range and medium-range NOEs and H[N] exchange rates, the secondary structure consists of four helices: helix 1 (3−29), helix 2 (33−48), helix 3 (78−101), and helix 4 (103−125). The [15]N, [1]HN, and [1]H[α] chemical shifts of the CO complex form are compared to those of the previously assigned oxidized (or ferric) state. From the chemical shift differences between these redox states, the orientation and the anisotropy of the paramagnetic susceptibility tensor have been determined using the crystallographic coordinates of the ferric state. The χ-tensor is axial, and the orientation of the z-axis is approximately perpendicular to the heme plane. The paramagnetic chemical shifts of the protons of the heme ligand have been determined and decomposed into the Fermi shift and dipolar shift contributions. Magnetic susceptibility studies in frozen solutions have been performed. Fits of the susceptibility data using the model of Maltempo (Maltempo, M. M. J. Chem. Phys. 1974, 61, 2540−2547) are consistent with a rather low contribution of the S = 3/2 spin state over the range of temperatures and confirm the value of the axial anisotropy. Values in the range 10.4−12.5 cm[-1] have been inferred for the axial zero-field splitting parameter (D). Analysis of the contact shift and the susceptibility data suggests that cytochrome c' of Rb. capsulatus exhibits a predominant high-spin character of the iron in the oxidized state at room temperature

Unusual Contact Shifts and Magnetic Tensor Orientation in Rhodobacter capsulatus Ferrocytochrome c': NMR, Magnetic Susceptibility, and EPR Studies

In contrast to high-spin ferrous paramagnetic heme proteins, the chemical shifts of the heme protons are very unusual in the ferrocytochromes c‘. Magnetic susceptibility studies of Rhodobacter capsulatus ferrocytochrome c‘ in frozen solutions have been performed and indicate an S = 2 spin state and a large negative axial (D) zero-field splitting parameter (−18.3 cm-1) as well as a significant rhombic (E) value (−4.9 cm-1). The 1H and 15N resonances have been extensively assigned by TOCSY−HSQC, NOESY−HSQC, and HSQC−NOESY−HSQC 3-D heteronuclear experiments performed on a 8 mM sample labeled with 15N. Based on short-range and medium-range NOEs and HN exchange rates, the secondary structure consists of four helices: helix-1 (3−30), helix-2 (34−49), helix-3 (78−97), and helix-4 (103−117). The 15N, HN, and Hα chemical shifts of the reduced (or ferro) state are compared to those previously assigned for the diamagnetic carbon monoxide complex form. From the chemical shift differences between these redox states, the orientation and the anisotropy of the paramagnetic susceptibility tensor have been determined using the crystallographic coordinates of the ferric state. Values of −23 and −3 cm-1 have been inferred for D and E, and the z-axis of the tensor is tilted approximately 30° from the normal to the heme. The paramagnetic chemical shifts of the heme protons have been determined and split up into Fermi shift and the dipolar shift contributions. The pattern of the contact shifts is very unusual, exhibiting a 2-fold symmetry, and is discussed in terms of molecular orbital interactions between the porphyrin macrocycle and the imidazole ring

Structural and Spectroscopic Insights into BolA-Glutaredoxin Complexes

International audienceBackground: BolA and glutaredoxin interact together in the iron metabolism. Results: They form two types of heterodimers with different binding surfaces depending on the presence or absence of an iron-sulfur cluster. Conclusion: The function of both proteins is likely modulated by the nature of the interaction. Significance: Understanding the molecular mechanisms responsible for iron sensing is crucial for all iron-mediated cellular processes. BolA proteins are defined as stress-responsive transcriptional regulators, but they also participate in iron metabolism. Although they can form [2Fe-2S]-containing complexes with monothiol glutaredoxins (Grx), structural details are lacking. Three Arabidopsis thaliana BolA structures were solved. They differ primarily by the size of a loop referred to as the variable [H/C] loop, which contains an important cysteine (BolA_C group) or histidine (BolA_H group) residue. From three-dimensional modeling and spectroscopic analyses of A. thaliana GrxS14-BolA1 holo-heterodimer (BolA_H), we provide evidence for the coordination of a Rieske-type [2Fe-2S] cluster. For BolA_C members, the cysteine could replace the histidine as a ligand. NMR interaction experiments using apoproteins indicate that a completely different heterodimer was formed involving the nucleic acid binding site of BolA and the C-terminal tail of Grx. The possible biological importance of these complexes is discussed considering the physiological functions previously assigned to BolA and to Grx-BolA or Grx-Grx complexes