Significance
The detection of ethanolamine (
N
H
2
C
H
2
C
H
2
OH) in a molecular cloud in the interstellar medium confirms that a precursor of phospholipids is efficiently formed by interstellar ...chemistry. Hence, ethanolamine could have been transferred from the proto-Solar nebula to planetesimals and minor bodies of the Solar System and thereafter to our planet. The prebiotic availability of ethanolamine on early Earth could have triggered the formation of efficient and permeable amphiphilic molecules such as phospholipids, thus playing a relevant role in the evolution of the first cellular membranes needed for the emergence of life.
Cell membranes are a key element of life because they keep the genetic material and metabolic machinery together. All present cell membranes are made of phospholipids, yet the nature of the first membranes and the origin of phospholipids are still under debate. We report here the presence of ethanolamine in space,
N
H
2
C
H
2
C
H
2
OH, which forms the hydrophilic head of the simplest and second-most-abundant phospholipid in membranes. The molecular column density of ethanolamine in interstellar space is
N
= (1.51
±
0.07)
×
10
13
c
m
−
2
, implying a molecular abundance with respect to
H
2
of
(
0.9
−
1.4
)
×
10
−
10
. Previous studies reported its presence in meteoritic material, but they suggested that it is synthesized in the meteorite itself by decomposition of amino acids. However, we find that the proportion of the molecule with respect to water in the interstellar medium is similar to the one found in the meteorite (
10
−
6
). These results indicate that ethanolamine forms efficiently in space and, if delivered onto early Earth, could have contributed to the assembling and early evolution of primitive membranes.
One of the proposed scenarios for the origin of life is the primordial RNA world, which considers that RNA molecules were likely responsible for the storage of genetic information and the catalysis ...of biochemical reactions in primitive cells, before the advent of proteins and DNA. In the last decade, experiments in the field of prebiotic chemistry have shown that RNA nucleotides can be synthesized from relatively simple molecular precursors, most of which have been found in space. An important exception is hydroxylamine, NH2OH, which, despite several observational attempts, it has not been detected in space yet. Here we present the first detection of NH2OH in the interstellar medium toward the quiescent molecular cloud G+0.693-0.027 located in the Galactic Center. We have targeted the three groups of transitions from the J = 2−1, 3−2, and 4−3 rotational lines, detecting five transitions that are unblended or only slightly blended. The derived molecular abundance of NH2OH is (2.1 0.9) × 10−10. From the comparison of the derived abundance of NH2OH and chemically related species, with those predicted by chemical models and measured in laboratory experiments, we favor the formation of NH2OH in the interstellar medium via hydrogenation of NO on dust grain surfaces, with possibly a contribution of ice-mantle NH3 oxidation processes. Further laboratory studies and quantum chemical calculations are needed to completely rule out the formation of NH2OH in the gas phase.
The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding the polymerization of amino acids. We have searched for this kind of ...compound toward the Galactic Center quiescent cloud G+0.693–0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH) with an abundance of ∼1 נ10−10. Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C2H5SH) with an abundance of ∼3 נ10−10, and we also detect methyl mercaptan (CH3SH) with an abundance of ∼5 נ10−9. Abundance ratios were calculated for the three SH-bearing species and their OH analogs, revealing similar trends between alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH3SH, and C2H5SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive Earth.
Abstract
Amines, particularly primary amines (R-NH
2
), are closely related to the primordial synthesis of amino acids since they share the same structural backbone. However, only a limited number of ...amines has been identified in the interstellar medium, which prevents us from studying their chemistry as well as their relation to prebiotic species that could lead to the emergence of life. In this Letter, we report the first interstellar detection of vinylamine (C
2
H
3
NH
2
) and tentative detection of ethylamine (C
2
H
5
NH
2
) toward the Galactic center cloud G+0.693-0.027. The derived abundance with respect to H
2
is (3.3 ± 0.4) × 10
−10
and (1.9 ± 0.5) × 10
−10
, respectively. The inferred abundance ratios of C
2
H
3
NH
2
and C
2
H
5
NH
2
with respect to methylamine (CH
3
NH
2
) are ∼0.02 and ∼0.008, respectively. The derived abundance of C
2
H
3
NH
2
, C
2
H
5
NH
2
, and several other NH
2
-bearing species are compared to those obtained toward high-mass and low-mass star-forming regions. Based on recent chemical and laboratory studies, possible chemical routes for the interstellar synthesis of C
2
H
3
NH
2
and C
2
H
5
NH
2
are discussed.
Context.
Theories of the origins of life propose that early cell membranes were synthesised from amphiphilic molecules simpler than phospholipids, such as fatty alcohols. The discovery in the ...interstellar medium (ISM) of ethanolamine, the simplest phospholipid head group, raises the question whether simple amphiphilic molecules are also synthesised in space.
Aims.
We investigate whether precursors of fatty alcohols are present in the ISM.
Methods.
To do this, we have carried out a spectral survey at 7, 3, 2 and 1 mm towards the Giant Molecular Cloud G+0.693-0.027 located in the Galactic centre using the IRAM 30 m and Yebes 40 m telescopes.
Results.
Here, we report the detection in the ISM of the primary alcohol
n
-propanol (in both conformers
Ga
-
n
-C
3
H
7
OH and
Aa
-
n
-C
3
H
7
OH), a precursor of fatty alcohols. The derived column densities of
n
-propanol are (5.5 ± 0.4) × 10
13
cm
−2
for the
Ga
conformer and (3.4 ± 0.3) × 10
13
cm
−2
for the
Aa
conformer, which imply molecular abundances of (4.1 ± 0.3) × 10
−10
for
Ga
-
n
-C
3
H
7
OH and of (2.5 ± 0.2) × 10
−10
for
Aa
-
n
-C
3
H
7
OH. We also searched for the
AGa
conformer of
n
-butanol
AGa
-
n
-C
4
H
9
OH without success, yielding an upper limit to its abundance of ≤4.1 × 10
−11
. The inferred CH
3
OH:C
2
H
5
OH:C
3
H
7
OH:C
4
H
9
OH abundance ratios are 1:0.04:0.006:≤0.0004 towards G+0.693-0.027, that is, they decrease roughly by one order of magnitude for increasing complexity. We also report the detection of both syn and anti conformers of vinyl alcohol, with column densities of (1.11 ± 0.08) × 10
14
cm
−2
and (1.3 ± 0.4) × 10
13
cm
−2
, and abundances of (8.2 ± 0.6) × 10
−10
and (9.6 ± 3.0) × 10
−11
, respectively.
Conclusions.
The detection of
n
-propanol, together with the recent discovery of ethanolamine in the ISM, opens the possibility that precursors of lipids according to theories of the origin of life, could have been brought to Earth from outer space.
The recently reported two-dimensional discrete perturbation theory for soft atomic fluids has been extended here for molecular fluids. In particular, the analytical expression for the Helmholtz free ...energy of intermolecular potentials of arbitrary profile is built within a discrete perturbation theory constructed with a sequence of two-dimensional (2D) square-well and square-shoulder potentials of variable effective widths and ranges. Fluids that comprised both convex and dumbbell particles have been considered. For the former ones, the equation of state was obtained as a function of density, temperature and intermolecular parameters with implicit shape dependence evaluated by a virial rescaling procedure from the compressibility factor of effective hard-disk and two-dimensional square-well/square-shoulder discrete potentials. By varying the intermolecular parameters through their geometrical dependence, some illustrative cases of 2D-square-well and Kihara spherocylinder fluids are explored, and their vapor-liquid phase diagrams and equations of state are tested against new simulation data. For the latter one, an available hard-dumbbell equation of state constitutes the reference term of the perturbation expansion. It is found that these theoretical approaches are able to reproduce the equations of state of the selected fluids quantitatively, but the vapor-liquid equilibrium is only grasped in a qualitative way. Reasons for this drawback are also discussed.
•A generalized two-dimensional discrete perturbation theory is developed for molecular fluids.•Phase diagrams and equations of state are tested against simulation data.•This theoretical framework can be easily updated after the report of new analytical theories for the liquid structure.•The theory can be extended to d-dimensional molecular fluids.
The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding the polymerization of amino acids. We have searched for this kind of ...compounds toward the Galactic Centre quiescent cloud G+0.693-0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH) with an abundance of ~ 1 × 10
−10
. Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C
2
H
5
SH) with an abundance of ~ 3 × 10
−10
, and we also detect methyl mercaptan (CH
3
SH) with an abundance of ~ 5 × 10
−9
. Abundance ratios were calculated for the three SH-bearing species and their OH-analogues, revealing similar trends between alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH
3
SH and C
2
H
5
SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive Earth.
Display omitted
•Two-photon absorption study of terpenoid-like chalcones derivatives.•First hyperpolarizability at 1064 nm of terpenoid-like chalcones derivatives.•Phenomenological approaches for ...two-photon absorption and first hyperpolarizability.•(Δμ01Evaluation of difference permanent dipole moment for non-fluorescent compounds.
Organic molecules exhibiting second and third-order nonlinear optical properties (NLOP) allow several applications in optics and photonics. Among the class of organic compounds, terpenoid-like chalcones derivatives constitute a suitable choice as nonlinear optical materials, given the possibility of obtaining a wide range of compounds that can be used in biophotonic applications. In this way, here we present a study of the first-order molecular hyperpolarizability and the two-photon absorption (2PA) cross-section of several terpenoid-like chalcones derivatives, aiming for applications in the therapeutic window. The 2PA spectra were evaluated employing the femtosecond tunable Z-Scan technique from 480 nm to 850 nm, and the first hyperpolarizability was determined at 1064 nm using the Hyper-Rayleigh scattering (HRS) technique. Moreover, the first-order molecular hyperpolarizability and the 2PA spectra were modeled by the sum-over-states (SOS) approach and undamped phenomenological model, respectively, providing new insights into the properties and compoundś structure relationship. Results showed that substituent features, such as electron-donating or withdrawing ability, were associated with the 2PA cross-section magnitude. Regarding HRS results, it was possible to compare the difference of state dipole moment from both approaches, combining two experimental routes to determine photophysical parameters of non-fluorescent compounds, revealing the structure-relationship aiming the increase of the NLOP at the near-infrared region.
Abstract
One of the proposed scenarios for the origin of life is the primordial RNA world, which considers that RNA molecules were likely responsible for the storage of genetic information and the ...catalysis of biochemical reactions in primitive cells, before the advent of proteins and DNA. In the last decade, experiments in the field of prebiotic chemistry have shown that RNA nucleotides can be synthesized from relatively simple molecular precursors, most of which have been found in space. An important exception is hydroxylamine, NH
2
OH, which, despite several observational attempts, it has not been detected in space yet. Here we present the first detection of NH
2
OH in the interstellar medium toward the quiescent molecular cloud G+0.693-0.027 located in the Galactic Center. We have targeted the three groups of transitions from the
J
= 2−1, 3−2, and 4−3 rotational lines, detecting five transitions that are unblended or only slightly blended. The derived molecular abundance of NH
2
OH is (2.1 ± 0.9) × 10
−10
. From the comparison of the derived abundance of NH
2
OH and chemically related species, with those predicted by chemical models and measured in laboratory experiments, we favor the formation of NH
2
OH in the interstellar medium via hydrogenation of NO on dust grain surfaces, with possibly a contribution of ice-mantle NH
3
oxidation processes. Further laboratory studies and quantum chemical calculations are needed to completely rule out the formation of NH
2
OH in the gas phase.
Abstract
The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding the polymerization of amino acids. We have searched for this kind ...of compound toward the Galactic Center quiescent cloud G+0.693–0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH) with an abundance of ∼1 × 10
−10
. Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C
2
H
5
SH) with an abundance of ∼3 × 10
−10
, and we also detect methyl mercaptan (CH
3
SH) with an abundance of ∼5 × 10
−9
. Abundance ratios were calculated for the three SH-bearing species and their OH analogs, revealing similar trends between alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH
3
SH, and C
2
H
5
SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive Earth.
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