A rotating fast bipolar wind and disk system around the B[e]-type star MWC 922.

We present interferometric observations with the Atacama Large Millimeter Array (ALMA) of the free-free continuum and recombination line emission at 1 and 3 mm of the "Red Square Nebula" surrounding the B[e]-type star MWC922. The unknown distance to the source is usually taken to be d=1.7-3 kpc. The unprecedented angular resolution ( up to ∼ 0 . ″ 02 ) and exquisite sensitivity of these data unveil, for the first time, the structure and kinematics of the emerging, compact ionized region at its center. We imaged the line emission of H30α and H39α, previously detected with single-dish observations, as well as of H51ϵ, H55γ, and H63δ, detected for the first time in this work. The line emission is seen over a full velocity range of ~180 km s-1 arising in a region of diameter < 0 . ″ 14 (less than a few hundred au) in the maser line H30α, which is the most intense transition reported here. We resolve the spatio-kinematic structure of a nearly edge-on disk rotating around a central mass of ~10 M ⊙ (d=1.7 kpc) or ~18 M ⊙ (d=3 kpc), assuming Keplerian rotation. Our data also unveil a fast (~100 km s-1) bipolar ejection (a jet?) orthogonal to the disk. In addition, a slow (<15 km s-1) wind may be lifting off the disk. Both, the slow and the fast winds are found to be rotating in a similar manner to the ionized layers of the disk. This represents the first empirical proof of rotation in a bipolar wind expanding at high velocity (~100 km s-1 ). The launching radius of the fast wind is found to be <30-51 au i.e., smaller than the inner rim of the ionized disk probed by our observations. We believe that the fast wind is actively being launched, probably by a disk-mediated mechanism in a (accretion?) disk around a possible compact companion. We have modelled our observations using the radiative transfer code MORELI. This has enabled us to describe with unparalleled detail the physical conditions and kinematics in the inner layers of MWC 922, which has revealed itself as an ideal laboratory for studying the interplay of disk rotation and jet-launching. Although the nature of MWC 922 remains unclear, we believe it could be a ~15 M ⊙ post-main sequence star in a mass-exchanging binary system. If this is the case, a more realistic value of the distance may be d~3 kpc.

Interferometric observations of SiO thermal emission in the inner wind of M-type AGB stars IK Tauri and IRC+10011.

CONTEXT: Asymptotic giant branch (AGB) stars go through a process of strong mass loss that involves pulsations of the atmosphere, which extends to a region in which the conditions are adequate for dust grains to form. Radiation pressure acts on these grains which, coupled to the gas, drive a massive outflow. The details of this process are not clear, including which molecules are involved in the condensation of dust grains. AIMS: We seek to study the role of the SiO molecule in the process of dust formation and mass loss in M-type AGB stars. METHODS: Using the IRAM NOEMA interferometer we observed the 28SiO and 29SiO J = 3 - 2, v = 0 emission from the inner circumstellar envelope of the evolved stars IK Tau and IRC+10011. We computed azimuthally averaged emission profiles to compare the observations to models using a molecular excitation and ray-tracing code for SiO thermal emission. RESULTS: We observe circular symmetry in the emission distribution. We also find that the source diameter varies only marginally with radial velocity, which is not the expected behaviour for envelopes expanding at an almost constant velocity. The adopted density, velocity, and abundance laws, together with the mass-loss rate, which best fit the observations, give us information concerning the chemical behaviour of the SiO molecule and its role in the dust formation process. CONCLUSIONS: The results indicate that there is a strong coupling between the depletion of gas-phase SiO and gas acceleration in the inner envelope. This could be explained by the condensation of SiO into dust grains.

Through the magnifying glass: ALMA acute viewing of the intricate nebular architecture of OH231.8+4.2.

We present continuum and molecular line emission ALMA observations of OH 231.8+4.2, a well studied bipolar nebula around an asymptotic giant branch (AGB) star. The high angular resolution ( ∼ 0 · ″ 2 - 0 · ″ 3 ) and sensitivity of our ALMA maps provide the most detailed and accurate description of the overall nebular structure and kinematics of this object to date. We have identified a number of outflow components previously unknown. Species studied in this work include 12CO, 13CO, CS, SO, SO2, QCS, SiO, SiS, H3O+, Na37Cl, and CH3OH. The molecules Na37Cl and CH3OH are first detections in OH 231.8+4.2, with CH3OH being also a first detection in an AGB star. Our ALMA maps bring to light the totally unexpected position of the mass-losing AGB star (QX Pup) relative to the large-scale outflow. QX Pup is enshrouded within a compact (≲60 AU) parcel of dust and gas (clump S) in expansion (V exp~5-7 km s-1) that is displaced by ∼ 0 · ″ 6 to the south of the dense equatorial region (or waist) where the bipolar lobes join. Our SiO maps disclose a compact bipolar outflow that emerges from QX Pup's vicinity. This outflow is oriented similarly to the large-scale nebula but the expansion velocities are about ten times lower (V exp≲35km s-1). We deduce short kinematical ages for the SiO outflow, ranging from ~50-80 yr, in regions within ~150 AU, to ~400-500 yr at the lobe tips (~3500 AU). Adjacent to the SiO outflow, we identify a small-scale hourglass-shaped structure (mini-hourglass) that is probably made of compressed ambient material formed as the SiO outflow penetrates the dense, central regions of the nebula. The lobes and the equatorial waist of the mini-hourglass are both radially expanding with a constant velocity gradient (V exp ∝ r). The mini-waist is characterized by extremely low velocities, down to ~1 km s-1 at ~150 AU, which tentatively suggest the presence of a stable structure. The spatio-kinematics of the large-scale, high-velocity lobes (HV lobes) and the dense equatorial waist (large waist) known from previous works are now precisely determined, indicating that both were shaped nearly simultaneously about ~800-900 yr ago. We report the discovery of two large (~8″×6″), faint bubble-like structures (fish bowls) surrounding the central parts of the nebula. These are relatively old structures although probably slightly (~100-200 yr) younger than the large waist and the HV lobes. We discuss the series of events that may have resulted in the complex array of nebular components found in OH 231.8+4.2 as well as the properties and locus of the central binary system. The presence of ≲80 yr bipolar ejections indicate that the collimated fast wind engine is still active at the core of this outstanding object.

The Abundance of SiC2 in Carbon Star Envelopes: Evidence that SiC2 is a gas-phase precursor of SiC dust.

CONTEXT: Silicon carbide dust is ubiquitous in circumstellar envelopes around C-rich AGB stars. However, the main gas-phase precursors leading to the formation of SiC dust have not yet been identified. The most obvious candidates among the molecules containing an Si-C bond detected in C-rich AGB stars are SiC2, SiC, and Si2C. To date, the ring molecule SiC2 has been observed in a handful of evolved stars, while SiC and Si2C have only been detected in the C-star envelope IRC +10216. AIMS: We aim to study how widespread and abundant SiC2, SiC, and Si2C are in envelopes around C-rich AGB stars and whether or not these species play an active role as gas-phase precursors of silicon carbide dust in the ejecta of carbon stars. METHODS: We carried out sensitive observations with the IRAM 30m telescope of a sample of 25 C-rich AGB stars to search for emission lines of SiC2, SiC, and Si2C in the λ 2 mm band. We performed non-LTE excitation and radiative transfer calculations based on the LVG method to model the observed lines of SiC2 and to derive SiC2 fractional abundances in the observed envelopes. RESULTS: We detect SiC2 in most of the sources, SiC in about half of them, and do not detect Si2C in any source, at the exception of IRC +10216. Most of these detections are reported for the first time in this work. We find a positive correlation between the SiC and SiC2 line emission, which suggests that both species are chemically linked, the SiC radical probably being the photodissociation product of SiC2 in the external layer of the envelope. We find a clear trend in which the denser the envelope, the less abundant SiC2 is. The observed trend is interpreted as an evidence of efficient incorporation of SiC2 onto dust grains, a process which is favored at high densities owing to the higher rate at which collisions between particles take place. CONCLUSIONS: The observed behavior of a decline in the SiC2 abundance with increasing density strongly suggests that SiC2 is an important gas-phase precursor of SiC dust in envelopes around carbon stars.

Treatment of Chronic Lower Extremity Ulcers with A New Er:Yag Laser Technology.

Chronic lower extremity ulcers (CLEUs) have a high prevalence and are difficult to treat due to their various aetiologies. The aim of this study is to evaluate the results achieved in treating CLEUs using an Erbium: YAG (Er:YAG) laser with RecoSMA technology. This laser emits thousands of microbeams of energy causing superficial epidermal ablation and a separation of dermal fibres due to a mechanical-acoustic and resonance effect. The evaluation of the results achieved was carried out by questionnaires completed by 18 patients enrolled in the study. Histological studies and photographs taken before each session (16 sessions in total) were analysed to visually monitor the clinical progress. The analyses were carried out with the help of computer software. The results after 16 treatment sessions showed the complete healing of ulcers or a decrease in their initial area of at least 55% in over 65% of the patients treated. The Student's t-test and Fisher's exact test were used for statistical analysis. The Er:YAG laser and RecoSMA technology ablates few epidermal cell layers, producing a mechanical-acoustic effect with resonance action leading to tissue regeneration mechanisms. This technology offers an effective and safe alternative for treating CLEUs.

High-resolution observations of IRAS 08544-4431: Detection of a disk orbiting a post-AGB star and of a slow disk wind.

AIMS: In order to study the effects of rotating disks in the post-asymptotic giant branch (post-AGB) evolution, we observe a class of binary post-AGB stars that seem to be systematically surrounded by equatorial disks and slow outflows. Although the rotating dynamics had only been well identified in three cases, the study of such structures is thought to be fundamental to the understanding of the formation of disks in various phases of the late evolution of binary stars and the ejection of planetary nebulae from evolved stars. METHODS: We present ALMA maps of 12CO and 13CO J=3-2 lines in the source IRAS 08544-4431, which belongs to the above mentioned class of objects. We analyzed the data by means of nebula models, which account for the expectedly composite source and can reproduce the data. From our modeling, we estimated the main nebula parameters, including the structure and dynamics and the density and temperature distributions. We discuss the uncertainties of the derived values and, in particular, their dependence on the distance. RESULTS: Our observations reveal the presence of an equatorial disk in rotation; a low-velocity outflow is also found, probably formed of gas expelled from the disk. The main characteristics of our observations and modeling of IRAS 08544-4431 are similar to those of better studied objects, confirming our interpretation. The disk rotation indicates a total central mass of about 1.8 M⊙, for a distance of 1100 pc. The disk is found to be relatively extended and has a typical diameter of ~ 4 1016 cm. The total nebular mass is ~ 2 10-2M⊙, of which ~ 90% corresponds to the disk. Assuming that the outflow is due to mass loss from the disk, we derive a disk lifetime of ~ 10000 yr. The disk angular momentum is found to be comparable to that of the binary system at present. Assuming that the disk angular momentum was transferred from the binary system, as expected, the high values of the disk angular momentum in this and other similar disks suggest that the size of the stellar orbits has significantly decreased as a consequence of disk formation.

The millimeter IRAM-30 m line survey toward IK Tau.

AIMS: We aim to investigate the physical and chemical properties of the molecular envelope of the oxygen-rich AGB star IK Tau. METHODS: We carried out a millimeter wavelength line survey between ~79 and 356 GHz with the IRAM-30 m telescope. We analysed the molecular lines detected in IK Tau using the population diagram technique to derive rotational temperatures and column densities. We conducted a radiative transfer analysis of the SO2 lines, which also helped us to verify the validity of the approximated method of the population diagram for the rest of the molecules. RESULTS: For the first time in this source we detected rotational lines in the ground vibrational state of HCO+, NS, NO, and H2CO, as well as several isotopologues of molecules previously identified, namely, C18O, Si17O, Si18O, 29SiS, 30SiS, Si34S, H13CN, 13CS, C34S, H234S, 34SO, and 34SO2. We also detected several rotational lines in vibrationally excited states of SiS and SiO isotopologues, as well as rotational lines of H2O in the vibrationally excited state ν2=2. We have also increased the number of rotational lines detected of molecules that were previously identified toward IK Tau, including vibrationally excited states, enabling a detailed study of the molecular abundances and excitation temperatures. In particular, we highlight the detection of NS and H2CO with fractional abundances of f(NS)~10-8 and f(H2CO)~[10-7-10-8 ]. Most of the molecules display rotational temperatures between 15 and 40 K. NaCl and SiS isotopologues display rotational temperatures higher than the average (~65 K). In the case of SO2 a warm component with Trot~290 K is also detected. CONCLUSIONS: With a total of ~350 lines detected of 34 different molecular species (including different isotopologues), IK Tau displays a rich chemistry for an oxygen-rich circumstellar envelope. The detection of carbon bearing molecules like H2CO, as well as the discrepancies found between our derived abundances and the predictions from chemical models for some molecules, highlight the need for a revision of standard chemical models. We were able to identify at least two different emission components in terms of rotational temperatures. The warm component, which is mainly traced out by SO2, is probably arising from the inner regions of the envelope (at ≲8R∗) where SO2 has a fractional abundance of f(SO2)~10-6. This result should be considered for future investigation of the main formation channels of this, and other, parent species in the inner winds of O-rich AGB stars, which at present are not well reproduced by current chemistry models.

ALMA high spatial resolution observations of the dense molecular region of NGC 6302.

CONTEXT: The mechanism behind the shaping of bipolar planetary nebulae is still poorly understood. It is becoming increasingly clear that the main agents must operate at their innermost regions, where a significant equatorial density enhancement should be present and related to the collimation of light and jet launching from the central star preferentially towards the polar directions. Most of the material in this equatorial condensation must be lost during the asymptotic giant branch as stellar wind and later released from the surface of dust grains to the gas phase in molecular form. Accurately tracing the molecule-rich regions of these objects can give valuable insight into the ejection mechanisms themselves. AIMS: We investigate the physical conditions, structure and velocity field of the dense molecular region of the planetary nebula NGC 6302 by means of ALMA band 7 interferometric maps. METHODS: The high spatial resolution of the 12CO and 13CO J=3-2 ALMA data allows for an analysis of the geometry of the ejecta in unprecedented detail. We built a spatio-kinematical model of the molecular region with the software SHAPE and performed detailed non-LTE calculations of excitation and radiative transfer with the shapemol plug-in. RESULTS: We find that the molecular region consists of a massive ring out of which a system of fragments of lobe walls emerge and enclose the base of the lobes visible in the optical. The general properties of this region are in agreement with previous works, although the much greater spatial resolution of the data allows for a very detailed description. We confirm that the mass of the molecular region is 0.1 M⊙. Additionally, we report a previously undetected component at the nebular equator, an inner, younger ring inclined ~60° with respect to the main ring, showing a characteristic radius of 7.5×1016 cm, a mass of 2.7×10-3 M⊙, and a counterpart in optical images of the nebula. This inner ring has the same kinematical age as the northwest optical lobes, implying it was ejected approximately at the same time, hundreds of years after the ejection of the bulk of the molecular ring-like region. We discuss a sequence of events leading to the formation of the molecular and optical nebulae, and briefly speculate on the origin of this intriguing inner ring.

Further ALMA observations and detailed modeling of the Red Rectangle.

AIMS: We aim to study the rotating and expanding gas in the Red Rectangle, which is a well known object that recently left the asymptotic giant branch (AGB) phase. We analyze the properties of both components and the relation between them. Rotating disks have been very elusive in post-AGB nebulae, in which gas is almost always found to be in expansion. METHODS: We present new high-quality ALMA observations of C17O J=6-5 and H13CN J=4-3 line emission and results from a new reduction of already published 13CO J=3-2 data. A detailed model fitting of all the molecular line data, including previous maps and single-dish observations of lines of CO, CII, and CI, was performed using a sophisticated code that includes an accurate nonlocal treatment of radiative transfer in 2D. These observations (of low- and high-opacity lines requiring various degrees of excitation) and the corresponding modeling allowed us to deepen the analysis of the nebular properties. We also stress the uncertainties, particularly in the determination of the boundaries of the CO-rich gas and some properties of the outflow. RESULTS: We confirm the presence of a rotating equatorial disk and an outflow, which is mainly formed of gas leaving the disk. The mass of the disk is ~ 0.01 M⊙, and that of the CO-rich outflow is around ten times smaller. High temperatures of ≳ 100 K are derived for most components. From comparison of the mass values, we roughly estimate the lifetime of the rotating disk, which is found to be of about 10000 yr. Taking data of a few other post-AGB composite nebulae into account, we find that the lifetimes of disks around post-AGB stars typically range between 5000 and more than 20000 yr. The angular momentum of the disk is found to be high, ~ 9 M⊙ AU km s-1, which is comparable to that of the stellar system at present. Our observations of H13CN show a particularly wide velocity dispersion and indicate that this molecule is only abundant in the inner Keplerian disk, at ≲ 60 AU from the stellar system. We suggest that HCN is formed in a dense photodissociation region (PDR) due to the UV excess known to be produced by the stellar system, following chemical mechanisms that are well established for interstellar medium PDRs and disks orbiting young stars. We further suggest that this UV excess could lead to an efficient formation and excitation of PAHs and other C-bearing macromolecules, whose emission is very intense in the optical counterpart.

A λ 3 mm and 1 mm line survey toward the yellow hypergiant IRC +10420: N-rich chemistry and IR flux variations.

AIMS: Our knowledge of the chemical properties of the circumstellar ejecta of the most massive evolved stars is particularly poor. We aim to study the chemical characteristics of the prototypical yellow hypergiant star, IRC +10420. For this purpose, we obtained full line surveys at 1 and 3 mm atmospheric windows. METHODS: We have identified 106 molecular emission lines from 22 molecular species. Approximately half of the molecules detected are N-bearing species, in particular HCN, HNC, CN, NO, NS, PN, and N2H+. We used rotational diagrams to derive the density and rotational temperature of the different molecular species detected. We introduced an iterative method that allows us to take moderate line opacities into account. RESULTS: We have found that IRC +10420 presents high abundances of the N-bearing molecules compared with O-rich evolved stars. This result supports the presence of a N-rich chemistry, expected for massive stars. Our analysis also suggests a decrease of the 12C/13C ratio from ≳ 7 to ~ 3.7 in the last 3800 years, which can be directly related to the nitrogen enrichment observed. In addition, we found that SiO emission presents a significant intensity decrease for high-J lines when compared with older observations. Radiative transfer modeling shows that this variation can be explained by a decrease in the infrared (IR) flux of the dust. The origin of this decrease might be an expansion of the dust shell or a lower stellar temperature due to the pulsation of the star.

A novel method of facial rejuvenation using a 2940-nm erbium:YAG laser with spatially modulated ablation: a pilot study.

The objective of this study was to determine the efficacy and safety of a novel method of facial rejuvenation using a 2940-nm erbium:YAG laser with Spatially Modulated Ablation™. A pilot study was performed in 16 women with moderate to severe signs of facial aging relative to chronological age, who underwent two treatment sessions with an Er:YAG laser coupled to the RecoSMA™ technology (Linline, Minsk, Belarus). The whole face was treated in all patients. Clinical efficacy, tolerance, adverse effects, complications, and histological changes due to the treatment were evaluated. Clinical photographs and biopsies were taken before treatment and 3 months after the second treatment session. All patients completed the study and presented no significant complications. Histological changes in the epidermis and dermis as a result of treatment were found. Fine lines, wrinkles, and overall facial aging improved significantly (p < 0.0001). The mean reduction of fine lines and wrinkles was 59 % (r = 40-75 %). The mean improvement of overall facial aging was 74 % (r = 55-90 %). After showing the patients the comparative photographs before and after treatment, 75 % of women stated that they were satisfied or very satisfied and would recommend the treatment. Preliminary results show an excellent safety/efficacy profile for this novel technology, which, based on observed results, can be considered to have advantages over other methods of facial rejuvenation with lasers.

Herschel/HIFI observations of the circumstellar ammonia lines in IRC+10216.

CONTEXT: A discrepancy exists between the abundance of ammonia (NH3) derived previously for the circumstellar envelope (CSE) of IRC+10216 from far-IR submillimeter rotational lines and that inferred from radio inversion or mid-infrared (MIR) absorption transitions. AIMS: To address the discrepancy described above, new high-resolution far-infrared (FIR) observations of both ortho- and para-NH3 transitions toward IRC+10216 were obtained with Herschel, with the goal of determining the ammonia abundance and constraining the distribution of NH3 in the envelope of IRC+10216. METHODS: We used the Heterodyne Instrument for the Far Infrared (HIFI) on board Herschel to observe all rotational transitions up to the J = 3 level (three ortho- and six para-NH3 lines). We conducted non-LTE multilevel radiative transfer modelling, including the effects of near-infrared (NIR) radiative pumping through vibrational transitions. The computed emission line profiles are compared with the new HIFI data, the radio inversion transitions, and the MIR absorption lines in the ν2 band taken from the literature. RESULTS: We found that NIR pumping is of key importance for understanding the excitation of rotational levels of NH3. The derived NH3 abundances relative to molecular hydrogen were (2.8 ± 0.5) × 10-8 for ortho-NH3 and [Formula: see text] for para-NH3, consistent with an ortho/para ratio of 1. These values are in a rough agreement with abundances derived from the inversion transitions, as well as with the total abundance of NH3 inferred from the MIR absorption lines. To explain the observed rotational transitions, ammonia must be formed near to the central star at a radius close to the end of the wind acceleration region, but no larger than about 20 stellar radii (1σ confidence level).

U-series dating of Paleolithic art in 11 caves in Spain.

Paleolithic cave art is an exceptional archive of early human symbolic behavior, but because obtaining reliable dates has been difficult, its chronology is still poorly understood after more than a century of study. We present uranium-series disequilibrium dates of calcite deposits overlying or underlying art found in 11 caves, including the United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage sites of Altamira, El Castillo, and Tito Bustillo, Spain. The results demonstrate that the tradition of decorating caves extends back at least to the Early Aurignacian period, with minimum ages of 40.8 thousand years for a red disk, 37.3 thousand years for a hand stencil, and 35.6 thousand years for a claviform-like symbol. These minimum ages reveal either that cave art was a part of the cultural repertoire of the first anatomically modern humans in Europe or that perhaps Neandertals also engaged in painting caves.

Estimation of free radical-quenching activity of leaf pigment extracts.

The chromogen 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) radical (ABTS.+) can be directly generated by the enzymatic system formed by hydrogen peroxide and horseradish peroxidase in ethanolic media. The reaction is time- and concentration-dependent, and the ABTS.+ generated shows excellent stability. The method is an adaptation of the decolouration method previously reported (Cano et al. 1998. Phytochem Anal 9:196-202), which was used for estimating anti-oxidant activity in aqueous media. When the assay described here was used to quantify the anti-oxidant activity of two anti-oxidants, Trolox (an analogue of vitamin E) and beta-carotene, the latter had 2.5 times better anti-oxidant capacity than Trolox at the same concentration. The free radical quenching activity (anti-oxidant activity) of leaf pigment extracts was measured and related to the the carotenoid contents in leaf extracts of barley, oat and citrus. The possibilities of using this experimental approach to evaluate the status of photoprotective pigments are discussed.

Nuclear planimetry in renal-cell tumors.

A morphometric study using conventional planimetry was carried out in 73 renal-cell tumors (64 adenocarcinomas and 9 adenomas) in order to correlate the objective nuclear measurements with some histologic and clinical data believed to have prognostic value. The use of a discriminant function to correctly separate adenomas and low-grade adenocarcinomas was also investigated. There was a strong association between the nuclear grade and the following parameters: nuclear area, nuclear major diameter and nuclear elongation. There was also a relationship between an adverse outcome and the major nuclear diameter and nuclear elongation. In a univariate survival analysis, only the clinicopathologic stage, the nuclear grade and the histologic presence of a pseudosarcomatous cell population had predictive value. Multivariate survival analysis using Cox models showed that the clinicopathologic stage, major nuclear diameter, presence of anaplastic cells and nuclear area had predictive value. Although the minor nuclear diameter reached a significant level, a discriminant function that would correctly separate adenomas and low-grade renal-cell carcinomas could not be formulated.

Proteolytic activity of the different fragments of factor B on the third component of complement (C3). Involvement of the N-terminal domain of Bb in magnesium binding.

Kinetic experiments measuring the proteolytic activity of Bb and 33Kd fragment (the C-terminal domain of factor B) on C3 were performed in several conditions, in order to assess the role of factor B domains in the catalytic activity and magnesium binding. The experiments were carried out in fluid phase with 125I-C3 or C3(H2O) as substrates and in the presence of nonradioactive C3b as cofactor. The results indicate: (a) The C-terminal domain, 33Kd, possesses proteolytic activity on C3, which is Mg2(+)-independent, whereas proteolysis by Bb is enhanced in 5 mM Mg2+. (b) C3b behaves as cofactor of 33Kd proteolytic activity on C3 and factor H is able to inhibit this activity. (d) Kinetics of C3 proteolysis by 33Kd shows a lag phase which is also displayed by Bb in the absence but not in the presence of Mg2+. Taken together these data are consistent with the involvement of the N-terminal domain of Bb in Mg2+ binding, which results in an enhancement of the proteolytic activity on C3 of the adjacent C-terminal domain. A C3 convertase model accounting for these results is presented.

Separation of active and inactive forms of the third component of human complement, C3, by fast protein liquid chromatography (FPLC).

C3(H2O), an inactive form of C3 present to a variable extent in most C3 preparations, has been isolated in 40 min from previously purified C3 using FPLC ion exchange chromatography on a Mono Q column. As many as six peaks were obtained from some C3 preparations, corresponding to different molecular forms of the protein. One of these peaks consisted of a molecular form of C3 with intact alpha and beta chains, a free sulfhydryl group but no hemolytic activity and was identified as C3(H2O). C3(H2O) eluted as a homogeneous peak well resolved from native C3, C3b, high molecular weight aggregates and small degradation fragments. The same C3(H2O) peak was generated from native C3 by repeated freeze-thaw cycles or NH2OH treatment. C3(H2O) alpha chain appeared as a doublet about 2 kDa heavier than native C3 alpha chain in low cross-linked gels. Two forms of C3b could be separated on the Mono S column, both able to form the C3 convertase. The present report describes a very fast method to resolve and isolate to homogeneity C3(H2O) and native C3 from C3 preparations. Both molecular forms of C3 are very suitable for studies of the initial and amplification C3 convertases of the alternative pathway of complement.

C3 binds covalently to the C gamma 3 domain of IgG immune aggregates during complement activation by the alternative pathway.

Ovalbumin-antiovalbumin IgG immune aggregates were incubated with normal human serum in the presence of iodo[1-14C]acetamide, in conditions in which only the alternative pathway of complement was activated. The [14C]C3b-IgG covalent complexes formed were digested with pepsin, and analysed by SDS/polyacrylamide-gel electrophoresis and fluorography. Covalent complexes of [14C]C3-Fd and [14C]C3-pFc' were visualized, demonstrating that, during complement activation by the alternative pathway, C3 is covalently incorporated into the C gamma 3 domain of IgG, as well as into the Fd region. The C gamma 2 domain becomes protected from pepsin action by the bound C3b. All the covalent linkages between C3 and the IgG were sensitive to hydroxylamine. When [14C]C3-pFc' covalent complexes were treated with 1 M-NH2OH and loaded onto a Bio-Gel P-4 column, a radioactive peak of 3 kDa was obtained. The material released from [14C]C3-pFc' and [14C]C3-F(ab')2 complexes after treatment with 1 M-NH2OH was mixed and analysed in the Bio-Gel P-4 column. A similar radioactive peak of 3 kDa was obtained. When this peak, either from [14C]C3-pFc' alone or from the mixture of [14C]C3-F(ab')2 and [14C]C3-pFc', was fractionated by h.p.l.c., virtually the same radioactive peptide profile was obtained, indicating that very similar C3 peptides remained covalently bound to both regions (Fab and C gamma 3) of the antibody molecule. It is suggested that C3 bound to the C gamma 3 domain of IgG may interfere with the Fc-Fc interactions of immune aggregates and thus may be involved in several biological properties displayed by these complement-activating aggregates.

Formation of covalent complexes between the fourth component of human complement and IgG immune aggregates.

The binding properties of activated C4 to immune complexes (ovalbumin-rabbit IgG antiovalbumin) were studied by using 125I-IgG in the immune complexes or performing the C4 binding assays in the presence of 14C-iodoacetamide. High molecular weight complexes formed between C4 and IgG could be detected by the incorporation of 14C-iodoacetamide in the -SH group generated in the nascent C4b during the activation process. The same complexes with an apparent molecular weight of 180,000 daltons were detected when the immune aggregates contained 125I-IgG. Two-dimensional SDS-PAGE analysis of the C4b-IgG covalent complexes indicated: In the absence of control proteins, the complexes are formed by the alpha'-chain of C4b and the H chain of the antibody. The alpha'-H complexes are 36% sensitive to hydroxylamine and 64% resistant. This is consistent with the presence of two populations of C4, which are not equivalent in their covalent binding with immune complexes. Covalent complexes C4-C4b or C4b(like)-C4b(like) are generated during the C4 activation and they are detected as alpha-alpha' or alpha-alpha complexes, respectively. Interaction of C4b with the L chain of the antibody molecule also seems to occur, but to a lesser extent than with the H chain.

The interaction of 1-anilino-8-naphthalene sulphonate with human C1q.

C1q has 12 binding sites for 1-anilino-8-naphthalene sulphonate (ANS), two per peripheral subunit. This number increases to 18 upon weak-acid-induced conformational transition in the globular heads. One ANS binding site is present in each C gamma 2 domain of human IgG. ANS is bound by C1q with a higher affinity (Ka = 2.07 X 10(6) M-1) than by the Fc fragment (Ka = 9.07 X 10(4) M-1) of human IgGl. Hence the inhibitory capacity of C1q binding to IgG immune complexes of ANS probably reflects its preferential binding to the globular heads of C1q. The characteristics of ANS-C1q binding may in part explain the hydrophobic component of the C1q-IgG interaction. It is suggested that an ionic-hydrophobic two-step process is involved in the contact between C1q and IgG.