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1.
The possibility of photoeradicating the prokaryotic microorganism Candida albicans by enhancing its endogenous porphyrin production and accumulation was investigated in this study. Induction of porphyrin
synthesis was performed by the addition of δ-aminolevulinic acid (ALA), or its hydrophobic derivative ALA methyl ester (m-ALA).
Photoinactivation of C. albicans was performed under blue light (407–420 nm) illumination. A decrease in viability of about 1.6 or 2.1 orders of magnitudes
was obtained with a light dose of 36 J/cm2 for an initial concentration of 100-mg/ml ALA or m-ALA, respectively. Endogenous porphyrins extracted from the cells showed
that cultures incubated with m-ALA accumulated a relatively higher amount of endogenous porphyrins than ALA, indicating better
transport through the yeast cell barriers. When a combination of miconazole and ketoconazole (antifungal agents) is given
at a sub-inhibitory concentration (0.5 μg/ml each) with an inducer, a 2.1 or 3.2 orders of magnitude decrease in viability
is caused with ALA or with m-ALA, respectively, upon illumination. Fluorescence intensities of the accumulated porphyrins
as demonstrated by FACS indicate that the combination of the two azole drugs and an inducer cause a relatively high amount
of endogenous porphyrins. Although the additive action of both azole drugs allow better penetration of the inducer, especially
m-ALA photoeradication remained limited because of an acidic pH generated in the presence of the inducer. The acidic pH is
probably the cause for the inefficiency of the photodynamic treatment. More hydrophobic inducers than m-ALA and less acidic
must be investigated to improve the photodynamic treatment by endogenous-induced porphyrins. 相似文献
2.
《Cryobiology》2020
As known for different metabolic functions, α-lipoic acid (ALA) has been tested for spermatozoa preservation of animals as well as of human, but not for fish spermatozoa. The present study determined the effects of ALA on short and long-term (cryopreservation) preservation of common carp (Cyprinus carpio) spermatozoa, for the first time. For that, spermatozoa were diluted in extenders containing 0 (control), 0.025, 0.05, 0.1, 0.5, 1, 2, 5, and 10 mM of ALA concentrations in both short-term preservation and cryopreservation. Spermatozoa motility parameters by computer-assisted semen analysis, viability, lipid peroxidation and catalase activity in spermatozoa were conducted in both 2nd and 120th hours of short-term storage and post-thaw samples. Higher percentages of total spermatozoa motility (80 ± 3) and viability (87 ± 3) were observed in 0.5 mM ALA group after 120 h of incubation. In post-thaw samples, higher percentages of these parameters were in 1 mM ALA group (74 ± 3 and 83 ± 2, respectively). Moreover, the results have shown that the addition of ALA until concentrations of 2 mM improved especially spermatozoa curvilinear velocity, maintained viability, and suppressed excessive lipid peroxidation during the preservations. In conclusion, the additions of 0.5 mM ALA for short-term preservation and 1 mM ALA for cryopreservation were the optimal concentrations, and shown the protective effects on common carp spermatozoa, when considering all measured parameters together. 相似文献
3.
Lorena Rodriguez Gabriela Divenosa Alcira Batlle Alexander Macrobert Adriana Casas 《Photochemical & photobiological sciences》2007,6(12):1306-1310
Aminolevulinic acid (ALA)-based photodynamic therapy (PDT) has been successfully employed in the treatment of certain tumours. Porphyrins endogenously generated from ALA induce tumour regression after illumination with light of an appropriate wavelength. The aim of this work was to compare porphyrin production from ALA and sensitivity to photodynamic treatment in a tumour/normal cell line pair. We employed the HB4a cell line from normal mammary luminal epithelium and its counterpart transfected with the oncogen H-Ras (VAL/12 Ras). After 3 h of exposure to ALA, HB4a-Ras cells produce a maximum of 150 ng porphyrins per 10(5) cells whereas HB4a produce 95 ng porphyrins per 10(5) cells. In addition, HB4a-Ras cells show a plateau of porphyrin synthesis at 1 mM whereas HB4a porphyrins peak at the same concentration, and then decrease quickly. This higher porphyrin synthesis in the tumorigenic cell line does not lead to a higher response to the photodynamic treatment upon illumination. Lethal doses 50, LD(50), determined by MTT assay were 0.015 J cm(-2) and 0.039 J cm(-2) for HB4a and HB4a-Ras respectively after 3 h exposure to 1 mM ALA. The conclusion of this work is that a tumour cell line obtained by transfection of the Ras oncogene, although producing higher porphyrin synthesis from ALA, is more resistant to ALA-PDT than the parental non-tumour line, however the mechanism is not related to photosensitiser accumulation, but very likely to cell survival responses. 相似文献
4.
Mechanisms of salt stress tolerance development in barley plants under the influence of 5-aminolevulinic acid 总被引:1,自引:0,他引:1
N. G. Averina E. R. Gritskevich I. V. Vershilovskaya A. V. Usatov E. B. Yaronskaya 《Russian Journal of Plant Physiology》2010,57(6):792-798
Growing barley (Hordeum vulgare L.) plants for 7 days on NaCl solutions (20–200 mM) decreased chlorophyll (Chl) a and b content with respect to that in untreated control plants. The content of free proline and the plant ability to synthesize
5-aminolevulinic acid (ALA) started to increase in parallel at salt concentrations of 20–50 mM. The maximum amount of ALA
accumulated in plants grown at 100 mM NaCl was twofold higher than in control plants grown on fresh water. In this case the
proline content increased 2.8-fold. On further increase in salt concentration, the rate of ALA accumulation decreased, approaching
control values at 150 mM NaCl; even lower rates were observed at 200 mM NaCl. The reduced ability to synthesize ALA was accompanied
by an increase in proline content. The albino tissue of plants treated at the seed stage with the antibiotic streptomycin
lost its ability to synthesize ALA needed for Chl formation. The proline content in the albino tissue was tenfold higher than
in control green plants and was 30-fold higher when the plants were grown on solutions with 100 mM NaCl. No effect of NaCl
on ALA-dehydratase activity was noted. As NaCl concentration was raised, there occurred the decrease in magnesium chelatase
activity, accumulation of reactive oxygen species (ROS), the increase in ascorbate peroxidase activity, and a slight decrease
in lipid peroxidation level. Growing plants in the presence of 150 mM NaCl and 10 or 60 mg/l exogenous ALA led to the increase
in proline content (by a factor of 1.8 and 4.2, respectively) and to the decrease in ROS content, in comparison with plants
grown on salt solutions without ALA. Furthermore, in the presence of exogenous ALA, the parameters of seedling growth became
similar to those of NaCl-untreated plants. The role of ALA in plants as an antistress agent is considered. ALA is supposed
to confer tolerance to salt stress by taking part in Chl and heme biosynthesis and also through functioning as a plant growth
regulator. A hypothesis is put forward that the impairment of ALA-synthesizing ability may redirect metabolic conversions
of glutamic acid from Chl and heme synthesis to the proline synthesis pathway, which would stimulate proline biosynthesis
and improve salt tolerance. 相似文献
5.
Masakazu Hara Ikuo Takahashi Michiyo Yamori Toru Tanaka Shigeyuki Funada Keitaro Watanabe 《Plant Growth Regulation》2011,64(3):287-291
5-Aminolevulinic acid (ALA) promotes the growth of plants by enhancing their photosynthetic activities, but there is little
information on how ALA influences the metabolism of sugars produced by photosynthesis. Here, we report the effects of ALA
on tissue growth, sugar content, and amylase activity in the radish taproot. 5-Aminolevulinic acid was applied with a foliar
spray (5.3–13,500 μM), and application at concentrations of 53, 530, and 2,700 μM enhanced the fresh weight of the taproot.
Glucose is a major soluble sugar of the radish taproot. 5-Aminolevulinic acid slightly increased the glucose content but did
not influence the fructose, sucrose, or starch contents. Radishes have β-amylase (RsBAMY1), which is expressed in the taproot.
5-Aminolevulinic acid enhanced both the amylase activity and the RsBAMY1 protein accumulation. These results suggest that
ALA may control starch accumulation by increasing the RsBAMY1 expression in the radish taproot. The relationship between taproot
growth and free sugar accumulation by ALA is also discussed. 相似文献
6.
5-Aminolevulinic acid (ALA), a precursor of porphyrin synthesis, increased the production of various porphyrin compounds in Candida guilliermondii cells. Metalloporphyrins and protoporphyrin IX (PPIX) were predominantly accumulated, respectively, at ALA concentrations of 0.2-0.4 mM and at those higher than 1.5 mM. 2,2;-Dipyridyl which complexed with bivalent metals significantly increased the content of endogenous PPIX even at ALA concentrations lower than 0.5 mM. Under these conditions, the yeast sensitivity to photodynamic effect of visible light (400-600 nm) dramatically increased due to photosensitization by endogenous PPIX. 相似文献
7.
Accumulating evidence, including experiments using cytochrome P450 1a2 (Cyp1a2) gene knock-out mice (Cyp1a2(−/−)), indicates
that the development of chemically induced porphyria requires the expression of CYP1A2. It has also been demonstrated that
iron enhances and expedites the development of experimental uroporphyria, but that iron alone without CYP1A2 expression, as
in Cyp1a2(−/−) mice, does not cause uroporphyria. The role of iron in the development of porphyria has not been elucidated.
We examined the in vivo effect of iron deficiency on hepatic URO accumulation in experimental porphyria. Mice were fed diets
containing low (iron-deficient diet (IDD), 8.5 mg iron/kg) or normal (normal diet (ND), 213.7 mg iron/kg) levels of iron.
They were treated with 3-methylcholanthrene (MC), an archetypal inducer of CYP1A, and 5-aminolevulinate (ALA), precursors
of porphyrin and heme. We found that uroporphyrin (URO) levels and uroporphyrinogen oxidation (UROX) activity were markedly
increased in ND mice treated with MC and ALA, while the levels were not raised in IDD mice with the same treatments. CYP1A2
levels and methoxyresorufin O-demethylase (MROD) activities, the CYP1A2-mediated reaction, were markedly induced in the livers of both ND and IDD mice
treated with MC and ALA. UROX activity, supposedly a CYP1A2-dependent activity, was not enhanced in iron-deficient mice in
spite of the fact of induction of CYP1A2. We showed that a sufficient level of iron is essential for the development of porphyria
and UROX activity. 相似文献
8.
Vitamins C and E improve regrowth and reduce lipid peroxidation of blackberry shoot tips following cryopreservation 总被引:2,自引:0,他引:2
Esther E. Uchendu Scott W. Leonard Maret G. Traber Barbara M. Reed 《Plant cell reports》2010,29(1):25-35
Oxidative processes involved in cryopreservation protocols may be responsible for the reduced viability of tissues after liquid
nitrogen exposure. Antioxidants that counteract these reactions should improve recovery. This study focused on oxidative lipid
injury and the effects of exogenous vitamin E (tocopherol, Vit E) and vitamin C (ascorbic acid, Vit C) treatments on regrowth
at four critical steps of the plant vitrification solution number 2 (PVS2) vitrification cryopreservation technique; pretreatment,
loading, rinsing, and regrowth. Initial experiments showed that Vit E at 11–15 mM significantly increased regrowth (P < 0.001) when added at any of the four steps. There was significantly more malondialdehyde (MDA), a lipid peroxidation product,
at each of the steps than in fresh untreated shoot tips. Vit E uptake was assayed at each step and showed significantly more
α- and γ-tocopherols in treated shoots than those without Vit E. Vit E added at each step significantly reduced MDA formation
and improved shoot regrowth. Vit C (0.14–0.58 mM) also significantly improved regrowth of shoot tips at each step compared
to the controls. Regrowth medium with high iron concentrations and Vit C decreased recovery. However, in iron-free medium,
Vit C significantly improved recovery. Treatments with Vit E (11 mM) and Vit C (0.14 mM) combined were not significantly better
than Vit C alone. We recommend adding Vit C (0.28 mM) to the pretreatment medium, the loading solution or the rinse solution
in the PVS2 vitrification protocol. This is the first report of the application of vitamins for improving cryopreservation
of plant tissues by minimizing oxidative damage. 相似文献
9.
Srđan Đ. Stojanović Vesna B. Medaković Goran Predović Miloš Beljanski Snežana D. Zarić 《Journal of biological inorganic chemistry》2007,12(7):1063-1071
Searching structures of porphyrin-containing proteins from the Protein Data Bank revealed that the π system of every porphyrin ring is involved in XH/π interactions, with most of the porphyrins having several interactions. Both five-membered pyrrole rings and six-membered
chelate rings are involved in XH/π interactions; the number of interactions with five-membered rings is larger than the number of interactions with six-membered
rings. We found interactions with C–H and N–H groups as hydrogen-atom donors; however, the number of CH/π interactions is much larger than the number of NH/π interactions. The amino acids involved in the interactions show a high conservation score. Our results that every porphyrin
is involved in XH/π interactions and that amino acids involved in these interactions are highly conserved demonstrate that XH/π interactions play an important role in porphyrin–protein stability.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Chunlei Li Hongmei Xu Jing Xu Xiaoya Chun Dejiang Ni 《Acta Physiologiae Plantarum》2011,33(3):973-978
Seedlings of Camellia sinensis (L.) were grown hydroponically to study the effect of aluminium (Al) on leaf antioxidant defence system and cell ultrastructure.
We found that malondialdehyde (MDA) content decreased at 0–0.32 mM Al, but increased significantly at 0.53 mM Al. Like MDA,
hydrogen peroxide (H2O2) content increased at 0.53 mM Al; however, no differences were observed at 0–0.32 mM Al. Superoxide dismutase (SOD, EC1.15.1.1)
activity remained practically constant at 0–0.32 mM Al, but increased sharply at 0.53 mM Al; catalase (CAT, EC1.11.1.6) and
guaiacol peroxidase (GPX, EC1.11.1.7) activities decreased following an initial increase, reaching their peaks at 0.32 mM
Al. Ascorbate peroxidase (APX, EC 1.11.1.11) activity increased and glutathione (GR, EC 1.6.4.2) level fluctuated with increasing
Al concentrations. Transmission electron microscope analysis of Al-treated leaves showed that although cell ultrastructural
integrity was maintained at 0–0.32 mM, significant membrane damage was observed at 0.53 mM. Our results suggest that at low
Al concentrations, the leaf antioxidant defence system can scavenge reactive oxygen species and sufficiently protect cells
from free radical injury. However, at higher Al concentrations (0.53 mM), the balance between formation and detoxification
of ROS is lost, resulting in the destruction of cell ultrastructure. 相似文献
11.
Recently, metal complexes of the isomers and analogs of porphyrin have become important model compounds for heme enzymes and proteins. While the chemistry of metalloporphyrins as heme models still attracts attention, the isomers and analogs of porphyrins provide insight into the biological choice of porphine as the macrocycle of choice and also help model reactive intermediates, such as high valent oxidation states. In this mini-review, we discuss the heme-relevant chemistry of N-confused porphyrin, an isomer of porphyrin with an inverted pyrrole ring, and focus on the chemistry of manganese, iron, and cobalt. The metallation chemistry of this macrocycle is more diverse than normal porphyrin, and involves tautomerization, C-H bond activation, the Lewis basicity of the external nitrogen, and issues with nucleophilic sensitivity. Despite the challenges posed by N-confused porphyrin, significant progress has been made toward generating heme-model complexes with this macrocycle. 相似文献
12.
Christoph Fertinger Alicja Franke Rudi van Eldik 《Journal of biological inorganic chemistry》2012,17(1):27-36
Compound I, an oxo–iron(IV) porphyrin π-cation radical species, and its one-electron-reduced form compound II are regarded as key intermediates in reactions catalyzed
by cytochrome P450. Although both reactive intermediates can be easily produced from model systems such as iron(III) meso-tetra(2,4,6-trimethylphenyl)porphyrin hydroxide by selecting appropriate reaction conditions, there are only a few thermal
activation parameters reported for the reactions of compound I analogues, whereas such parameters for the reactions of compound
II analogues have not been investigated so far. Our study demonstrates that ΔH
≠ and ΔS
≠ are closely related to the chemical nature of the substrate and the reactive intermediate (viz., compounds I and II) in epoxidation
and C–H abstraction reactions. Although most studied reactions appear to be enthalpy-controlled (i.e., ΔH
≠ > −TΔS
≠), different results were found for C–H abstractions catalyzed by compound I. Whereas the reaction with 9,10-dihydroanthracene
as a substrate is also dominated by the activation enthalpy (ΔH
≠ = 42 kJ/mol, ΔS
≠ = 41 J/Kmol), the same reaction with xanthene shows a large contribution from the activation entropy (ΔH
≠ = 24 kJ/mol, ΔS
≠ = −100 J/kmol). This is of special interest since the activation barrier for entropy-controlled reactions shows a significant
dependence on temperature, which can have an important impact on the relative reaction rates. As a consequence, a close correlation
between bond strength and reaction rate—as commonly assumed for C–H abstraction reactions—no longer exists. In this way, this
study can contribute to a proper evaluation of experimental and computational data, and to a deeper understanding of mechanistic
aspects that account for differences in the reactivity of compounds I and II. 相似文献
13.
N. A. Filatova K. M. Kirpichnikova N. D. Aksenov E. A. Vakhromova I. A. Gamaley 《Cell and Tissue Biology》2011,5(5):463-470
The tumor growth of murine hepatoma cells MH22a treated with N-acetylcysteine (NAC, 10 mM) and alpha-lipoic acid (ALA, 1.25
mM) antioxidants or hormone melatonin (1 μM) and transplanted into syngeneic (C3HA) mice has been studied. NAC, ALA, or melatonin
treatment for 20 h reduced the tumor development and the number of dead mice. Melatonin produced the most pronounced effect.
Tumors appeared in 10 days in 100% of control mice injected with untreated cells; the injection of cells pretreated by NAC
or ALA generated tumors in 40 and 53% of mice, respectively. Cells pretreated with melatonin produced tumors 18–20 days after
injection; 67% of control mice died in 36 days (the observation period). The mortality rate was 20 and 53% if the injected
cells were treated with NAC or ALA, respectively. No mice died during this period with melatonin-pretreated cells. We found
that treatment with antioxidants delayed (NAC) or completely inhibited (ALA) the progression of the cell cycle of murine hepatoma
cells. After the antioxidant removal, the cell cycle was restored. Melatonin did not affect the cell cycle phase distribution.
We conclude that there is no direct correlation between the loss of tumorigenic properties and the altered proliferative activity
of hepatoma cells. Different mechanisms of antioxidants and melatonin action that underlie the transient normalization of
the tumor phenotype are discussed. 相似文献
14.
The influence of alanine on plasma amino acid concentrations and fuel substrates as well as cycling performance was examined.
Four solutions [6% alanine (ALA); 6% sucrose (CHO); 6% alanine and 6% sucrose (ALA–CHO); an artificially sweetened placebo
(PLC)] were tested using a double-blind, randomised, cross-over design. During each trial, ten cyclists ingested 500 mL of
test solution 30 min before exercise and 250 mL after 15, 30, and 45 min of exercise. Participants cycled for 45 min at 75%
VO2max followed by a 15-min performance trial. Blood was collected before beverage consumption and prior to the performance trial.
Alanine concentration was increased (p < 0.05) by approximately tenfold for ALA and ALA–CHO and less than twofold for CHO and PLC. Alanine ingestion increased concentrations
of most gluconeogenic amino acids. Overall, alanine supplementation tended to produce favourable metabolic effects, but did
not influence performance. 相似文献
15.
Yoval-Sánchez B Jasso-Chávez R Lira-Silva E Moreno-Sánchez R Rodríguez-Zavala JS 《Journal of bioenergetics and biomembranes》2011,43(5):519-530
Ethanol is one of the most efficient carbon sources for Euglena gracilis. Thus, an in-depth investigation of the distribution of ethanol metabolizing enzymes in this organism was conducted. Cellular
fractionation indicated localization of the ethanol metabolizing enzymes in both cytosol and mitochondria. Isolated mitochondria
were able to generate a transmembrane electrical gradient (Δψ) after the addition of ethanol. However, upon the addition of
acetaldehyde no Δψ was formed. Furthermore, acetaldehyde collapsed Δψ generated by ethanol or malate but not by D-lactate.
Pyrazole, a specific inhibitor of alcohol dehydrogenase (ADH), abolished the effect of acetaldehyde on Δψ, suggesting that
the mitochondrial ADH, by actively consuming NADH to reduce acetaldehyde to ethanol, was able to collapse Δψ. When mitochondria
were fractionated, 27% and 60% of ADH and aldehyde dehydrogenase (ALDH) activities were found in the inner membrane fraction.
ADH activity showed two kinetic components, suggesting the presence of two isozymes in the membrane fraction, while ALDH kinetics
was monotonic. The ADH Km values were 0.64–6.5 mM for ethanol, and 0.16–0.88 mM for NAD+, while the ALDH Km values were 1.7–5.3 μM for acetaldehyde and 33–47 μM for NAD+. These novel enzymes were also able to use aliphatic substrates of different chain length and could be involved in the metabolism
of fatty alcohol and aldehydes released from wax esters stored by this microorganism. 相似文献
16.
Six different extracellular laccase isoforms were identified in submerged cultures of the commercially important edible mushroom,
Coprinus comatus. Although laccase activity (~55 IU/L) was readily detectable in unsupplemented control cultures containing 1.6 μM Cu2+ after 22-day incubation, mean enzyme levels (~150–185 IU/L) were 2.7–3.4-fold higher in cultures supplemented with 0.5–3.0 mM
Cu2+. Laccase production was also stimulated by Mn supplementation over the range 0.05–0.8 mM Mn2+, and the peak value of ~225 IU/L recorded after 22 days in cultures containing 0.8 mM added Mn2+ was 4.5-fold higher compared with unsupplemented controls. Of 12 aromatic compounds tested for their effect on laccase isozyme
production by C. comatus, highest laccase levels (~188 IU/L), equivalent to a 4.4-fold increase compared with unsupplemented controls (~43 IU/L),
were recorded after 22 days in cultures supplemented with 3.0 mM caffeic acid. Other aromatic compounds tested all stimulated
laccase production, with peak enzyme levels 1.3–3.3-fold higher compared with unsupplemented controls. Extracellular laccase
levels in cultures supplemented with optimal concentrations of Mn2+ and caffeic acid together were 38% and 15% lower, respectively, compared with cultures containing the separate supplements.
Lac1 was the most abundant laccase isoform produced under all the conditions tested, but marked differences were observed
in the production patterns of Lac2–Lac6. 相似文献
17.
The influence of 2,2′-dipyridyl (2,2′-DP) on the activity of one of the enzymes at the initial stages of chlorophyll (Chl)
biosynthesis, δ-aminolevulinic acid dehydratase (ALAD; δ-aminolevulinate hydro-lyase, EC 4.2.1.24), as well as on δ-aminolevulinic
acid (ALA) accumulation was investigated in green barley (Hordeum vulgare L.) leaves. In seven-day-old green leaves treated with 3 mM 2,2′-DP for 17 h in darkness and subsequently irradiated with "white
light" (15 W m-2) for 4, 8, and 24 h the ALAD activity was 51 % as compared to that in untreated leaves. At the same time,
the ALA forming system was most sensitive to the photodynamic processes caused by 2,2′-DP. After 8 h of irradiation, ALA synthesis
was entirely inhibited. After the treatment the leaves accumulated exceptionally high amounts of Chl precursors such as protoporphyrin
IX (Proto), Mg-protoporphyrin IX (Mg-Proto), its monomethyl ester, and protochlorophyllide (Pchlide) that are photosensitizers
of photodynamic processes in plants. A comparatively low Chl and carotenoid (Car) destruction was registered during the subsequent
4 and 8 h of irradiation. At the same time, the content of Chl precursors was negligible. The low photodestruction of Chl
and Car included in pigment-protein complexes, against the background of fast porphyrin disappearance, and fast decrease of
enzymatic activities at the initial stages of Chl production could mean that the photodynamic effect induced by porphyrins
accumulated in the presence of 2,2′-DP affected first the Chl enzymatic system and did not change the pool of already synthesized
photosynthetic pigments.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Periplasmic metal binding protein characterized by high histidine content was cloned from moderate halophile, Chromohalobacter salexigens. The protein, termed histidine-rich metal binding protein (HP), was expressed in and purified from E. coli as a native form. HP bound to Ni- and Cu-loaded chelate columns with high affinity, and Co- and Zn-columns with moderate
affinity. Although the secondary structure was not grossly altered by the addition of 0.2–2.0 M NaCl, the thermal transition
pattern was considerably shifted to higher temperature with increasing salt concentration: melting temperature was raised
by ~20 °C at 2.0 M NaCl over the melting temperature at 0.2 M NaCl. HP showed reversible refolding from thermal melting in
0.2–1.15 M NaCl, while it formed irreversible aggregates upon thermal melting at 2 M NaCl. Addition of 0.01–0.1 mM NiSO4 stabilized HP against thermal melting with high reversibility, while addition above 0.5 mM resulted in irreversible melting
due to aggregation. 相似文献
19.
The primo-vascular (Bonghan) tissue has been identified in most tissues in the body, but its structure and functions are not
yet well understood. We characterized electrophysiological properties of the cells of the primo-nodes (PN) on the surface
of abdominal organs using a slice patch clamp technique. The most abundant were small round cells (~10 μm) without processes.
These PN cells exhibited low resting membrane potential (−36 mV) and did not fire action potentials. On the basis of the current–voltage
(I–V) relationships and kinetics of outward currents, the PN cells can be grouped into four types. Among these, type I cells
were the majority (69%); they showed strong outward rectification in I–V relations. The outward current was activated rapidly
and sustained without decay. Tetraethylammonium (TEA) dose-dependently blocked both outward and inward current (IC50, 4.3 mM at ±60 mV). In current clamp conditions, TEA dose-dependently depolarized the membrane potential (18.5 mV at 30 mM)
with increase in input resistance. The tail current following a depolarizing voltage step was reversed at −27 mV, and transient
outward current like A-type K+ current was not expressed at holding potential of −80 mV. Taken together, the results demonstrate for the first time that
the small round PN cells are heterogenous, and that, in type I cells, TEA-sensitive current with limited selectivity to K+ contributed to resting membrane potential of these cells. 相似文献
20.
V. D. Rumyantseva E. A. Aksenova O. N. Ponamoreva A. F. Mironov 《Russian Journal of Bioorganic Chemistry》2000,26(6):423-428
We found that thionyl chloride can chlorinate porphyrin complexes with transient metals (Pd, Ni, or Cu) at the free β andmeso-positions of the porphyrin macrocycle. A more prolonged or rigorous treatment also causes the chlorination of side alkyl
substituents, mainly, methyl groups. 相似文献