Link
17-Black Natural Conductors
www.tightrope.it/nicolaus/index.htm
.
Black
is everywere, on earth and in stellar interspaces. Black is melanin, no
matter what the extensively conjugated carbonium skeleton was formed from.
Melanin is a conductor as it is a radical-polarone. It is a stable free
radical, holding positive charges, balanced by counter anions and exhibiting a
small gap, 1,4 eV. Experimental data, molecular modelling studies and
molecular quantum mechanics calculations agree describing DHI-melanin, as a
structure fundamentally constituted by repetitive units of
5-gem-diol-indol-6-one linked at 4,7 positions. Linear filaments in two
low-energy conformational states, helix and alternate sheet, can arrange to
form stratum and cage by further
C2 bonds, taking in account for gas and ion keeping and metal chelate
formation. Electric
and conformational properties explain different roles of melanins. As UV
filter and radical scavenger black has a protective function in epithelial
tissue; in dopaminergic neurons of Substantia nigra, an area of brain
involved in fine motor control, it can act as a conductor allowing rapid
electron passage which, generating a magnetic field, can feel the earth-field
and control movements. Melanin destruction, in Parkinson’s disease can
participate to symptoms and development of neuro-degenerative process.
Many
others pigments are found in nature and are candidates to
semiconductivity or superconductivity 24 like
biline derivatives, metalloporphyrins, ommins, pterins,
pheomelanins ( link 9 ), pheochromes, benzothiazines, benzothiazinones,
dibenzothiazinones indigoids, cyanines, humic acids, fulvic acids etc..All the
pigments are radical-polarones with the characteristic polyconjugate chain of
acetilene-black.
A
revision of the biological, chemical, and physical properties of the natural
pigments is desiderable.
……………………………………..…..
As
reported by Raper1,2 in 1927 melanin is formed by action of
tyrosinase on tyrosine. Many products of the process tyrosine--melanin have
been isolated or identified like DOPA, dopachrome, cyclodopa,
5,6-dihydroxyindole (DHI), 5,6-dihydroxyindole-2-carboxylic acid (DHICA).The
process of melanogenesis of the DHI which seems to occur in Sepia although
conflicting with experimental date is generally accepted.
Besides
melanin, carbon dioxide and H2O2 are also
produced.
The
role played by H2O2 in melanogenesis was not undertaken.
Carbon
dioxide arises from heating of many melanins but its significance
remains uncertain2,8. DHI-melanin prepared in the presence of
catalase, by heating, produces CO2 (4.7%)
Four
possibilities exist for eumelanins to explain carbon dioxide evolution:
a.
CO2 could arises from DHICA, Dopachrome or Cyclodopa
units although is known that the carboxylic group is firmly bound in these
substances,
b.
CO2 arises from COOH groups formed from the breakdown of catechol
units. 8
c.
CO2 arises from gem-diols groups.
d.
CO2 arises from the cationic center of the polymer.
More
recently3,30 it was found that the melanin precursor in Sepia
is DHI . In other words DHI-melanin would represent an interesting model for
melanin structure studies.Unfortunately theory don’t agree with experiment
sepiomelanin having many carboxylic groups
( cyclodopa units ? ).
Analytical results showed by different authors are variable depending to the
melanin extraction and purification method adopted .The most frequently
reactions occuring during extraction and purification of melanosome and
premelanosome34 are :
a.
oxidative degradations
b.
decarboxylation
c.
condensation
d.
copolymerization
e.
modification of the counteranion16
Numerous
papers fail in describing the elemental composition of the melanin 2,
4, 6, 8, 11, 33. All the proposed structures have, for each indole
unit, one oxygen less than the requirement of analytical results. Numerous
adjustments have been claimed, included the presence of water molecules,
DHICA or Dopachrome units, indole and benzene breakdown forming COOH groups23,
etc., to justify the differences between found and calculated values of the
elemental composition.
In
this paper, the 5-gem-diol-indol-6-one structure is proposed, as a repetitive
unit of the precursor to explain analytical data and chemical-physical
behaviour.
Actually,
elemental analysis of DHI-melanin and sepiomelanin, a well known pigment from
Sepia officinalis6,7,8,27 are in apparent agreement with
polymers containing units
(Table 1) with one more oxygen atom
that there is in the precursor.
Table 1
Elemental
Composition of DHI-melanin, sepiomelanin and its derivatives. 20,31
Samples
Found %
DHI-melanin
8
C, 58.8 H, 3.3 N, 9.3
DHI-melanin
4,5,30
C, 55.3 H, 3.2 N, 8.3
DHICA-melanin
27
C, 56.1 H, 3.1 N, 7.6
Sepiomelanin6,7,8,33
C, 59.9 H, 3.4 N, 8.2
DHI-melanin
methyl ether8
C, 61.6 H, 5.7 N, 8.6 OCH3, 21.5
Sepiomelanin
methyl ether 8
C,64.1 H, 5.5 N, 7.4 OCH3, 18.5
Calculated %
(C8H3O2N
)x
C, 66.2 H, 2.1 N, 9.6
polyindolequinone
(DHI-quinone)
(C9H3O4N)
C, 57.1 H, 1.6 N, 7.4
polyindolquinone-2-carboxyl
(DHICA-quinone)
(C8H5O3N
)x
C, 58.9 H, 3.0 N, 8.5
polyindolequinone
monohydrate
(C8H7O4N)x
C, 53.0 H, 3.8 N, 7.7
polyindolequinone
dihydrate
(C9H7O3N)x
C, 61.0 H, 4 N, 7.9 OCH3, 17.5
polyindolequinone
monohydrate
methyl
ether
(C10H1004N)
C, 57.7 H, 4.8 N, 6.7 OCH3, 29.8
polyindolequinone
monohydrate
dimethyl
ether
(C10H504N)
C, 59.4 H, 2.4 N, 6.9 OCH3, 15.3
polyindolequinone-2-carboxylic
ester
(DHICA-quinone)
Methylation
reaction, by diazomethane, suggests the presence of a methoxy group on each
indole, in contrast with proposed
structures. This contrast has been resolved by a conformational study on
oligomers formed by units linked
in4-7 in the
preferential sites of polymerization reaction
In the structure considered an hydroxyl group
is available to methylation, but the oligomers
stabilized by hydrogen bonds assume two low energy conformations: an alternate
sheet and the more stable helix. A 60° dihedral angle between two indole
planes is formed.
Torsional
angles and formation heats are reported. Constrained by steric hindrance, the
alternated pleated sheet and the helix are held in their shapes by hydrogen
bonds between a hydroxyl group and the heterocyclic NH. The hydroxyl group
over (or under) the indolic plane and the heterocyclic NH generates a helix,
whereas a bond between the hydroxyl group alternatively over and under the
indole plane and the heterocyclic NH determines the alternate pleated sheet.
Many
different equilibria of quinone and reduced forms of monomers and
oligomers may occur in the process of melanogenesis. The equilibrium
water-quinone,quinone-quinone hydrated, dopachrome-DHICA,
decarboxydopachrome-DHI were not
considered at present.
Currently,
it is not possible to establish when the gem-diol formation take place ,even
if after or before polymerization. Nevertheless, ab initio quantum-mechanical
calculations indicate that the 5-gem-diol is more, about 13 Kcal, stable than
the corresponding 6-gem-diol and that the orbital coefficients (LUMO) of
indole-5,6-dione make the 5-carbon the more suitable to water nucleophilic
attack.
Hydration
of quinone carbonyl groups of indole 5,6-dione, resulting on the 5-gem-diol is
a less studied process and it is very similar to hydration of ketone compounds19.
This reaction is favoured by electron-withdrawing groups like the a-b
unsaturated
system and the condensed pyrrolic ring of indol-5,6-dione. The hydrogen bond
formation between the pyrrolic NH of an indole unit and a 5-hydroxyl group on
the next indole unit can further stabilize the 5-gem-diol formation.
Thermogravimetric
analysis of dried natural sepiomelanin and synthetic DHI-melanin showed that
water is removed at a transition temperature of 96.4° (about 10%), according
to a quinone monohydrate structure 36.
Actually,
if DHI-melanin held a polyindolquinone structure, according to the
widespread hypothesis reported in literature 2,11 a very easy
reduction reaction and high stability to oxidation should be expected, whereas
melanin is a substance sensible to oxygen, oxidizing agents and halogens and
is not reducible with quinone typical reducing agents and catalytic hydrogen.
Reactivity
of other positions of DHI can be responsible of a further link between the
polymeric chains to form sheaf stratum or cage structure (Figure 3). This
structure explains the water, gas, ions, organic and inorganic products, high
binding affinity of melanins.
Figures
shows the melanin structure together with the acetylene black, which
can be considered an un-substituted melanin.
In
all melanins, the unpaired electrons (one of two hundred indole units
calculated on the EPR signal), the positive charges (one per eight units
calculated on the amount of the counteranion; Cl- in sepiomelanin)
distributed along the unsaturated, conjugated skeletons, the red line (the
spine, a conductive wire into the molecule)) are responsible of their
conductivity.24-26,29,30
Biological
electrical fields may be generated by the spine changing the
superficial properties of the pigment. This would be an ideal equipment for
cell assembly and cell movement. The system would be easily removed by H2O2.
Investigation
on natural melanins recovered from human tumors and on synthetic DHI-melanin,
demonstrated that the black pigment, acting as a semiconductor, responds to a
critical applied field by changing its conductivity and that the nature of
response depends on hydration and temperature of the melanin sample and on
external circuity. Drying-hydration equilibrium determinates the switching
properties of melanins ( The WEB Advances
: Organic Semiconductor ) suggesting that
’‘ strongly linked
‘’ water is involved in melanin conductivity. The electronic
characteristics persist in intact melanosomes.12,13
This
result and the discovery that melanin responds dynamically to electric field
behaving as semiconductor and that this property is connected to hydration are
in agreement with the description of DHI-melanin as polyindolquinone
monohydrated .
Physical
models of natural colours based on measurements of the optical costants
of eumelanin and pheomelanin ( Link 14 )
are known. Using the results of exact Mie calculations of the
scattering and absorption cross-sections for individual pigment granules we
show that the colors produced by dispersions of eumelanin or pheomelanin
granules are strongly dependant on the pigment granules size. Measurements of
the granule size distribution in hair of differing colors are consistent with
the predictions.The colors are found to be strongly dependant on the
Mott-Davis optical energy gap parameter
EO
which controls the dispersion of the optical costant
k in amorphous semiconductor. Changes in EO
as small as 0.2 eV,out of 1.4 eV,
are sufficient
to alter color from brown to red hair. Moreover, black color, interpreted on
the basis of band theory indicates a gap value about of 1.5 eV, according to a
black crystalline semiconductor like SeS.
Acetylene,
pyrrole, benzene blacks seem to share common properties; their
structural peculiarities may identify a new class of organic semiconductor
substances.
DHI,
adrenaline, serotonine, tryptamine, dopamine, isoquinoline15 blacks
may be also present in nature and can play interesting but still unknown
biological roles.
Figure
4 reports a representation of melanin whose backbone arranges in
alternate-sheet and helix giving rise to cages. Water plays a crucial role
stabilizing secondary and tertiary structures and promote a cooperative
phenomenon where hydrogen-bonding is a cohesive interaction. Hydrated indole
units may determine the self-assembly of melanin and its pH dependent
aggregation, organizing water, or squeezing it out from the internal cages.
Folding of the helix backbone upon itself could form spheres, stretched-out
zigzag chains and build strata.
As
radical-polarone materials, melanins are radical scavengers acting as UV
radical-filters in epithelial tissue and bio-organic conductors, allowing a
rapid electron passage through the polyconjugated skeleton, ( the
red line of the figures, acetylene-black ) An electric conductor in
crucial area of brain, could also induce magnetic fields useful to feel the
earth's field and to control movements.
Neuromelanin11
the granular black pigment, present in bio-electrical
active neurons can be associated
with Parkinson’s disease. In fact, biological reactions involving
radicals (OH. in Fenton reaction) and nucleophilic attacking agents can easily
react on radical and cationic sites, of melanin producing different
occurrences iron depletion, local carbon hybrid changes, variations of the
conformational structures and fall of conductivity deteriorating the switching
functions.
Melanin
structure associated with the
radical-polarone system of acetylene-black , identify a biological conductors
class of large interest in many scientific fields and open doors to still
unexplored territory of neurosciences where variations of conformational
structure and falls of conductivity dominate together with potential
gradients, electron flows and charge transfer processes.
--------------------------------
Melanin
extraction :
To
avoid the formation of certain artifacts (oxidation products of H2O2
) we have recently adopted the following procedure for extraction and
purification of sepiomelanin :
The
animal was frozen to death. The black material was gently squeezed from ink
sac (about 500 mg for each sac) and an excess of
catalase physiological
solution was added to freshly
recovered crude pigment to destroy H2O2 present
(about 175 mg). and the mixture frozen for 48 h. New catalase was
added,the mixture was homogenized and
centrifuged repeatedly with a NaCl physiological, degassed, solution to take
away protein components (10’at
5.000 to 15.000g to be tested; granules are taken at low centrifuge speed )
and separate melanosome from granules. Precipitate was washed by
centrifugation three times with H2O, three times with aceton (10
ml), deionised, degassed water obtaining
A (
sepiomelanin or Ca Mg salt of sepiomelanic acid ).
A
is washed many times with 2N HCl ( pure reagent ) to remove
calcium and magnesium ions.
Supernatant fractions combined and lyophilised were investigated for C, H, N,
Ca, Mg, cyclodopa, DHI,
DHICA, pyrrolic acids.
The
black solid residue was suspended in degassed, deionised water and pH
adjusted to 10 by 1N NaOH solution and was sonicated (15’, 80 W) keeping
temperature at 0 °C . The suspension was filtered under nitrogen and the
black solution was acidified at pH 1 by pure HCl conc. and
centrifuged.The precipitate containing a quasi protein-free sepiomelanin
acid, washed very well with water
is kept moist in refrigerator.
The
black material is additioned with pure HCl conc., maintained for one
night in the dark. was dilute and
centrifuged and washed many times with deionized water,acetone, water.
The
material B
(sepiomelanic acid) so obtained is kept moist and deep frozen.
For
analysis the pigment is dried in vacuo at room temperature and equilibrated in
air of a cleaned-air room.
---------------------------------------------------
Elemental
analysis for A
(sepiomelanin) obtained at 5000 g
C,
H, N, S, Ca.
Mg, Zn, Cu, Ni, Fe, Cl ( the counteranion sometimes ), ashes.
Same analysis for
fraction obtained at 10000g and 15000g
Elemental
analysis for B
(sepiomelanic acid ) :
C,
H, N, S, Zn, Cu, Cl, Ni, Fe,
ashes.
The
same analysis is repeated with sepiomelanin-methylether (diazomethane)
together with OCH3% determination.
Melanin
salts of Fe, Cu, Ni, Zn, are prepared from sonicated solutions at neutral pH
and analyzed for elemental composition and conductivity.
Research
of the counterion is carried out.
Analytical
values obtained with this procedure are in agreement with values calculated
for C8H4NO3 or C17H6N2O6
units.
Physical
parameters to determine:
EPR,
Conductivity, PMGE (Proctor and McGinness effect) , superconductivity, doping
effect, MALDI, IR, NMR, X-rays, binding capacity for ions and organic
products, gas adsorbing, cellular assembling capacity.
A
similar procedure may be followed for other melanins.Sometimes the procedure
may be simplified because the melanin is soluble in water, dilute ammonia or
alkalies ( pheomelanins, allomelanins, humic acids, plant melanins,
microrganism-melanins). Sonication (80
W for 15 min. in alkaline solution ) is sometimes recommended.
--------------------------------------
Fig. 1
Fig. 2
A
B
B’
Fig. 3
ELECTRICAL WAVES
IN NATURE
History
Animal
Electricity , Galvani
1777
The
band structure of melanins, Pullman
1954
Switching
in melanins, Proctor and McGinness
1972
---------------------------
J.E.McGinness,
J.E.Corry, P.Proctor, ‘’
Amorphous semiconductor switching
in melanins ‘’ Science, 183, 853-854, 1974.
drp@drproctor.com
The WEB ‘’Advances
: Organic Semiconductors
Biological
pigments are amorphous semiconductors (
Science, 177, 896, 1972 ) Melanin
produced synthetically and isolated from biological systems act as an
amorphous semiconductor threshold switch. Switching occurs reversibly as
potential gradients two to three orders of magnitude lower than reported for
inorganic thin films, and comparable to gradients existing in some biological
systems. Of a number of other biological materials tested , only cytochrome c
acted similarly, but at the high potential gradients reported for thin film
amorphous semiconductors
From
the Solid state Physics Correspondent
. Nature, 248, 475, 1974 :
…..Now
at least one biological material
has been shown to have a strikingly large conductivity when corrected excited.
Mc Ginness,Corry and Proctor, of the University of Texas Cancer Center,
Houston, report in Science 1974, that melanins
can be made to switch from
a poorly conducting to to a higly
conducting state at fairly low electric fields ( say from 10K ohm-cm to 100
ohm-cm at a field of 300 V cm-1 ). This remarkable phenomenon occurs both in
melanin made synthetically from tyrosine and in that extracted from a human
melanoma. The large conduction is not destructive in any way and is reversible
; According to some tests
conduction seems to be electronic rather
ionic
……
---------------------------
G. de Santillana ‘’ Alessandro Volta ‘’ Scientific American, 212, 82-92, 1965
His
pile or battery opened the age of electrical
power and settled his celebrated argument with Luigi Galvani.Curiously
he then played no part in the epocal developments that his invention made
possible.
(
Born Como 1745 dead Como 1827 ).
( Luigi Galvani born Bologna 1737 dead Bologna 1798 )
Galvani
and Volta were long in dispute over what Galvani called ‘’ animal
electricity ‘’ and
Volta called ‘’ metallic
electricity ‘’.
-----------------------------
W.
Grey Walter ‘’
The Electrical Activity of the Brain
‘’ Scientific American, reprinted from June 1954.
By
recording the pulsation of tiny currents from various parts of the head the
electroencephalographer diagnose brain disorders and studies the basic
mechanism of mind
.
------------------------------
W.Holmes ‘’ Le variazioni cromatiche nei cefalopodi ‘’ Endeavour, 14,78-82, 1955.
Quando nel corso dell’evoluzione i cefalopodi
abbandonarono la protezione di una conchiglia, svilupparono la curiosa facoltà
protettiva di potere cambiare
rapidamente disposizione dei colori sul loro corpo.Questi cambiamenti sono
dovuti alla contrazione e al rilasciamento dei cromatofori controllati dal
sistema nervoso. Ulteriori ricerche su questo fenomeno potranno gettare luce
sulla correlazione tra l’organizzazione del tessuto nervoso ed il
comportamento
-----------------------------------
R.D.Keynes ‘’ La produzione di elettricità nei pesci ‘’ Endeavour, 15, 215-222, 1956.
Esistono diverse specie di pesci, per lo più marini
capaci di produrre elettricità
------------------------------------
N.Millott, ‘’ La fotosensibilità animale, particolarmente nelle forme prive di occhi’’ Endeavour, 16, 19-28, 1957
Biosensori.
-------------------------------------
H.W.Lissmann,
‘’ Electric location by fishes ‘’
Scientific American, reprint from March 1963
It is
well known that some fishes generate strong electric
fields to stun their prey
or discourage predators.Gymnarchus niloticuc produce
a weak field to the purpose of sensing its environment.
--------------------------------------
W.A.Little
‘’ Superconductivity
at room temperature ‘’
Scientific American, 212, 21-27, 1965.
Little’s
organic materials and polyacetilene-black system are present in melanins ,
porphyrins and other natural pigments.
---------------------------------------
References
1.
Raper, H.S. The tyrosinase-tyrosine reaction. VI. Production from tyrosine of
5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid, the precursor
of melanin. Biochem.
J. 21, 86-96 (1927).
2.
Nicolaus,R.A.,Melanins,Hermann,Paris(1968). : http://www.tightrope.it/nicolaus/index.htm
3.
Palumbo,
A., Di Cosmo, A., Gesualdo, I., Hearing, V.J., Subcellular localization and
function of melanogenic enzymes in the ink gland of sepia officinalis. Biochem.
J. 323,749-756 (1997)
4.
Ito, S., Reexamination of the structure of eumelanin. BBA., 883, 155-161
(1986)
5.
Beer,R.J.S., Broadhurst,T., Robertson, A. The chemistry of melanins.Part V.
The autoxidation of 5,6-Dihydroxyindoles. J.
Chem. Soc., 1947-1953 (1954)
6.
Panizzi, L., Nicolaus,R., Ricerche sulle Melanine, Gazz.Chim. Ital.
82,435-460, (1952).
7.
Piattelli, M.& Nicolaus, R.A., The structure of melanins and melanogenesis.
I. The structure of melanin in Sepia. Tetrahedron, 15, 66-75
(1961).
8.
Piattelli, M., Fattorusso, E., Magno, S.& Nicolaus, R.A. The strucure of
melanins and melanogenesis. II. Sepiomelanin and synthetic pigments.
Tetrahedron, 18, 941-949 (1962).
9.
MOPAC (version 6.0) available from Quantum Chemistry Program Exchange, No.
455. Vinter, J. G.; Davis, A.; Saunders, M. R. Strategic Approaches to Drug
Design. 1. An Integrated Software Framework for Molecular Modelling. J. Comput.-Aided
Mol. Design, 1, 31-55 (1987). Treasurywala, A. M.; Jaeger, E. P.,
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Chem. 17, 1171-1182 (1996).
10.
Kienz, E., Jellinger, K., Stachelberger, H. & Linert, W. Iron as catayst
for oxidative stress in the pathogenesis o f
Parkinson's dease? Life Sci,. 65, 1973-1976 (1999)
11.
Prota, G., Melanins and melanogenesis , AP, San Diego (1992).
12.
McGinness, J.E., Corry, P., Proctor. P. Amorphous semiconductor switching in
melanins. Science
183, 853-854 (1974). www.organicsemiconductors.com
13.
Kirkpatrick,D.S.,
McGinness, J.E., Moorhead, W.D., Corry, P.M., Proctor, P.H. Melanin-water-Ion
Dielectric Interactions. Pigment
Cell, Vol. 4, 257-262, Karger, Basel (1979)
. The
WEB (
Advances :
Organic
Semiconductors ).
14.
Becke, A. D. Phys. Rev. A 38, 3098-3100 (1988). Lee, C., Yang, W. & Parr,
R. C. Phys. Rev. A 37, 785-789 (1988).
15.
Mosca, L., Blarzino, C., Coccia, R., Foppoli, C. & Rosei, M.A. Melanins
from tetrahydroisoquinolines: spectroscopic characteristics, scavenging
activity and redox transfer properties. Free Radical Biology & Medicine,
24, 161-7 (1998).
16.
All the data accumulated in the past half century lead to an unreal picture of
melanins function and structure. No research of counteranion has been
undertaken.
17.
Melanins are particles and not molecules. For all that literature swarms with
papers on molecular weight of melanins. Some authors quoted a molecular
wlight between 500 and 30000 Da.
18.
We propose to assign the igNobel award 2002 to the discovery of melanin
molecular weight. Candidates names will be comunicated later.
19. Ogata, Y. & Kawasaki A. The chemistry
of the carbonyl group 3-10. Ed Zabicky, J. Interscience Publishers, London
1970.
20. Presence of ashes and counteranions may
alter the results.
21. Kroesche, C., Peter, M.G., Detection of
Melanochromes by MALDI-TOF Mass Spectrometry, Tetrahedron, 52, 3947-3952
(1996).
22. Bertazzo,A., Costa, C., Allegri, G.,
Seraglia,R., Traldi,P., Biosinthesys of Melanin from Dopamine.An investigation
of Early oligomerization Products, Rapid.Comm. Spectrom. 9, 634-640
(1995).
23. The catecholic fission of indole units (sepiomelanin)
may be obtained with alkaline H2O2. The compound isolated as Barium salt C20H17N3O15Ba3
is the precursor of pyrrolic acids (6),(28). This polyacid was also
found in MALDI spectra (Napolitano, A., et al. Rapid. Comm. Mass Spectrom. 10,
204, 468 (1996).
24. Nicolaus, B.J.R., Nicolaus, R.A.
Speculating on the band colours in Nature, Atti Accademia Pontaniana, XLV,
365-385, ( 1996 ).
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26.
Nicolaus, R.A., Parisi, G., The Nature of Animal Blacks. Atti
Accademia Pontaniana XLIX, 197-233 (2000).
27.
Piattelli, M., Fattorusso, E., Magno, S., Nicolaus, R.A. The structure of
Melanins and melanogenesis-III-The structure of sepiomelanin, Tetrahedron 19,
2061-2072 (1963).
28. Nicolaus, R.A., MALDI mass spectrometry and
melanins, Rend. Acc. Sci. Fis. Mat., LXIV, 315-323 (1997)
29. Nicolaus, G., Nicolaus, R.A., Melanins,
Cosmoids, Fullerenes, Rend.Acc.Sci.Fis.Mat. LXVI, 131-158, (1999).
30. Olivieri, M., Nicolaus, R.A., Sulla
DHI-melanina, Rend. Acc. Sci. Fis. Mat. LXVI,
85-96 (1999).
31. Results are influenced by extraction and
purification methods adopted. Frequently the black material
32.
A tetramer of DHICA has been found in tapetum lucidum of cuttlefish
(Ito, S., et al., Biochem. J., 161, 207-217, 1974 ) but the material was not
adequately characterized.
33.
Benathan, M., Contribution a l'analyse quantitative des melanines, These de
Doctorat, Faculte des Sciences, Lausanne, 1-140, Lausanne (1980).
34.
Bolognese, A., Nicolaus, R.A., About the structure of sepiomelanin, Atti
Accademia Pontaniana, Vol. XLIX, 309-312, (2001).
35. Bolognese, A., Nicolaus, R.A., Melanins and
Pheomelanins, Atti Accademia Pontaniana, Vol. L,
in press.
36.
Nicolaus, R.A., Bolognese, A., Conduttori biologici neri. Atti Accademia
Pontaniana, Vol. L,
in press.
37.
Nicolaus,B.J.R.,Nicolaus,R.A., Olivieri,M., Riflessioni sulla Chimica della
materia nera interstellare, Rend. Acc.Sci.Fis.Mat. LXVI, 113-129 (1999)
38.
Nicolaus,B.J.R., Lo scrigno oscuro della vita, Atti della Accademia Pontaniana,
XLVIII, 355-380, (1999).
------------------------
Consultant
Board:
bologne@cds.unina.it
rnicolaus@tightrope.it
http://www.tightrope.it/nicolaus/index.htm
gparisi@cds.unina.it
bruno.nicolaus@virgilio.it
bnicolaus@icmib.na.cnr.it
Naples,
April 2001.
Revised September 2003