Tin tetrachloride interaction with human hemoglobin

In the presence of tin tetrachloride, the rate constant for the rebinding of CO to the triliganded hemoglobin, l'4, is much increased and the number of molecules participating in the CO ligation is decreasing. The pH drops, but a proton consumption process also takes place at the same time. The heme and its environment do not seem to change much, but the tin complexing to protein is very probable. The oxidation of hemoglobin in the form of either oxy or carbonmonoxy occurs with rather high rate.

Oxygen effect in the radiolysis of proteins. III. Haemoglobin

Radiolysis of haemoglobin was carried out in phosphate buffer under air, N2 or N2O and with and without ethanol. Radiation products were separated by SDS-PAGE. The loss of subunits and simultaneous aggregation and fragmentation of haemoglobin was measured, if OH-radicals were unscavenged. There was no sensitizing effect of oxygen on the degradation process. Radiation-induced fragmentation was not a random process, but produced specific fragments. The estimated molecular weights of these fragments gave further support to the assumption that the aminoacyl-proline peptide group is the preferential breaking site if OH radicals react with proteins in the presence of oxygen. In contrast with lactate dehydrogenase and bovine serum albumin such fragmentation was observed not only after aerobic radiolysis but also under anaerobic conditions. This difference must be caused by the Feporphyrin system which reacts with H2O2 under release of oxygen. If haemoglobin was irradiated under air the yield of aggregates was much lower than under N2O or N2.

[Nonenzymatic covalent modification of human hemoglobin by pyridoxal-5-phosphate under the effect of visible light]

Under the action of visible light, PLP with apo-, oxy- and deoxy-Hb at 4-20 degrees C and neutral pH produced adducts stable to dialysis and Sephadex gel filtration. The stable adduct formation enhanced with an increase in radiation intensity and/or irradiation time. Under light, production of stable adducts occurred most effectively for apo-Hb and was significantly slowed down in the case of met-Hb as well as in the presence of an electron acceptor, methylene blue. PLP-Hb adducts possessed intense fluorescence coinciding in properties with the fluorescence of stable PLP adducts obtained after Schiff base reduction by NaBH4. Stable adduct formation is assumed to proceed owing to Schiff base aldimin link reduction by photoejected electrons. During isoelectrofocusing of hemoglobins which had formed stable adducts with PLP under light or after NaBH4 treatment of solutions, essentially the same pictures were observed as to the number of new bands and their position in the isoelectroforegram, with the band intensity being different. This is related to the distinctions in the electron seeking properties of the Schiff bases produced by PLP with alpha-NH2 groups of Val-1 and epsilon-NH2 groups of lysine residues of the protein alpha- and beta-chains.

[Serotonin as a photoprotector of the oxygen-transporting function of hemoglobin]

Oxygen-binding properties of human hemoglobin modified by UV-light (240-400 nm) in dose range (1.51 + 6.04) x 10(2) J/m2 together with serotonin (10(-4) M) has been studied by means of spectrophotometry. UV-radiation results in increase of the oxygen affinity of hemoglobin. Serotonin displays the photoprotective effect on the hemoglobin oxygen-transport function. Mechanisms of photoprotection of the biogenic amine are proposed for discussion.

A pulsed photolysis procedure for determining oxygen equilibrium parameters of low-affinity noncooperative hemoglobins

It is often very difficult to obtain precise values for oxygen equilibrium constants for low-affinity noncooperative hemoglobins owing to the ease with which they are oxidized and denatured with even the most gentle stirring or agitation. We have developed a procedure that eliminates this problem by maintaining the hemoglobin as HbCO except during the brief time it is present as Hb, and HbO2 forms following photolysis. Oxygen is continuously removed by an enzyme system. The solution is photolyzed to 100% every 2-3 min during the deoxygenation process to obtain maximum absorbance changes at the Hb-HbCO isosbestic. These maximum absorbance changes at known times during the deoxygenation provide the necessary data for obtaining the oxygen equilibrium constant. These absorbance changes are used with enzyme kinetics equations to obtain calculated times. The simple equations, which neglect heme concentration, will be satisfactory for nearly all conditions, but for generality the complete equations are given. The variance minimizations are with respect to observed and calculated photolysis times. The results for native carp Hb over a range of temperatures are in excellent agreement with results obtained with considerably more material and greater difficulty by other methods.

Fractal analysis of photolysis of nitrosyl haemoglobin at low temperatures

Photolysis of nitrosyl haemoglobin (HbNO) has been studied from 5.9 K to 20 K for R, T and RT conformations. It was observed that the experimental curves have two different behaviours at a given temperature in a particular conformation. At shorter time scales the data are well reproduced by a model based on fractal concepts, where the relevant parameter is the difference between the fractal dimension and the fraction. For simplicity at longer time scales a simple exponential was used to fit the curves.

Heme-CO religation in photolyzed hemoglobin: a time-resolved Raman study of the Fe-CO stretching mode

Time-resolved resonance Raman spectroscopy has been employed to monitor geminate heme-CO rebinding in photolyzed HbCO. The excitation frequency was tuned to enhance the scattering from rebound heme sites 20-500 ns subsequent to CO photolysis. The behavior of vFe-C during ligand rebinding has important ramifications concerning heme pocket dynamics of the distinct equilibrium configurations of the six-coordinate heme sites. During the geminate phase of recombination, the Fe-CO bond strengths and configurations of the rebound sites (inferred from the positions and line widths of vFe-C) were found to be the same as those of equilibrium configurations of HbCO within 500 ns of CO photolysis for all samples. No evidence was found for the existence of transient metastable configurations during geminate recombination. Spectra obtained at earlier times (100 ns) revealed small differences in the geminate rebinding rates of the two equilibrium configurations. Since there is little or no further CO rebinding between 100 and 500 ns after photolysis, some interconversion must occur between the dominant HbCO configurations on a submicrosecond time scale.

Characterization of pulsed-dye laser-mediated vasodilatation in a rabbit femoral artery model of vasoconstriction

Vasoconstriction is a clinical problem associated with invasive vascular procedures, microvascular reconstruction and subarachnoid hemorrhage. We sought to characterize the ability of pulsed-dye laser irradiation to reverse and prevent vasoconstriction in an anesthetized rabbit model of surgically and pharmacologically induced vasoconstriction. Five groups of experiments were performed to study the effect of pulsed-dye laser irradiation delivered through a 320 microns core ball-tip fiber into the femoral artery. The studies demonstrated that pulsed-dye irradiation can reproducibly cause vascular dilatation. The zone of vasodilatation propagated equally proximal and distal to the site of irradiation within the vessel. When saline was infused into the vessel to replace flowing blood during delivery of laser irradiation, no significant vasodilatation occurred. After laser irradiation reversed surgical and pharmacologic vasoconstriction, the vessel was resistant to further pharmacologic vasoconstriction. This resistance to pharmacologic vasoconstriction did not occur if the vessel was pharmacologically predilated before delivery of laser irradiation. Pathologic analysis of the vessels revealed endothelial damage and mild to moderate medial necrosis, most significant at the site of energy delivery. These studies provide characterization of pulsed-dye laser-mediated vasodilatation in an in vivo model. Delivery of pulsed-dye laser energy has potential clinical application and warrants further investigation.

In vitro and in vivo ultraviolet-induced alterations of oxy- and deoxyhemoglobin

Ultraviolet (UV) radiation was found to convert oxyhemoglobin and deoxyhemoglobin stoichiometrically into methemoglobin and a met-like product, respectively. The peak conversion efficiency for oxyhemoglobin occurred at 285 nm and decreased by a factor of 100 by 315 nm. The peak conversion efficiency for deoxyhemoglobin occurred at 290 nm and decreased by a factor of 30 by 320 nm. The transformation of oxyhemoglobin to methemoglobin was also documented in intact erythrocytes using UV-B radiation. Finally, similar transformations were found to occur in human skin with UV-B exposure but not on all volunteers tested. These results imply that methemoglobin will be formed in vivo on solar exposure and provide evidence that UV-B photons reach the blood vessels.

[The photodestruction of hemoglobin]

It was shown that hemoglobin photodestruction occurs in the process of light absorption by protein globin, as well as by its hem. Quantum yields of photoreactions decreased with the increase of irradiation wave length. We observed two mechanisms of photodestruction: dependent and independent on the existence of the dissolved oxygen in solution. Hemoglobin photodestruction due to hem absorption did not exist in the absence of dissolved oxygen.

E.p.r. studies of photolysis of nitrosyl haemoglobin at low temperatures: effects of quaternary structure

Photolysis of nitrosyl haemoglobin (HbNO) has been studied from 6.5 K to 20 K for different NO saturation conditions. The kinetic curves are fitted equally well by a biphasic exponential and a distribution of activation energies. The parameters are straightforwardly related to the quaternary structure of the protein. The biphasic model indicates that two germinate processes in the NO reassociation to Hb dominate at low temperatures independent of the protein conformation.

Effects of irradiation on red cells stored in CPDA-1 and CPD-ADSOL (AS-1)

Red blood cells (pRBC) collected in citrate, phosphate, dextrose, adenine-formula 1 (CPDA-1) and citrate, phosphate, dextrose-adenine, manitol saline solution (CPD-ADSOL [AS-1]) anticoagulants are increasingly being stored for variable periods in transfusion service inventories following irradiation. While anecdotal reports of increased K+ following irradiation and storage have recently appeared in the literature, concomitant in vitro biochemical changes resulting from differences in anticoagulants have not been reported. Utilizing two venipunctures, two units each of 225 mL of blood from five volunteers were collected in anticoagulant-adjusted CPDA-1 and AS-1 bags. Within two hours of collection, each unit was equally divided. One of each pair was irradiated (2000 rads). Samples were analyzed on Days 0, 1, 3, 7, and every seven days to expiration. Irradiation resulted in a 2.3 fold increase in K+ during the first seven days of storage for both anticoagulants, although significantly greater K+ levels were observed in the CPDA-1 pairs compared to the AS-1 pairs. Comparison of glucose utilization, plasma free hemoglobin, 2,3-diphosphoglycerate (2,3-DPG) and lactate dehydrogenase between control and irradiated CPDA-1 and AS-1 pairs and between anticoagulants were documented.

Study of the clinical thermoluminescent dosimeter in the direct measurement of radiation adsorbed dose for radioimmunotherapy

One of the major obstacles facing radioimmunotherapy (RIT) is the lack of a device to measure directly tumor and normal tissue radiation absorbed dose. Calculations based on the clearance and imaging scans have several limitations; hence we design and fabricate a sheathed clinical thermoluminescent dosimeter (TLD) for the measurement of absorbed dose by implantation in humans. Preclinical studies are performed in nine normal rabbits. Complete blood count, body temperature monitoring, clinical observation and necropsy show no untoward effects from the TLD. Consistent bone marrow radiation doses are noted in the four rabbits receiving 131I-labeled monoclonal antibody A6H. By using up to 20 clinical TLDs in one sheath, it will be possible to determine macroscopic heterogeneities in organs undergoing RIT.

What is the importance of anaemia in radiotherapy? The value of animal studies

It has been recognised for many years that anaemic cancer patients have a particularly poor prognosis (see recent reviews [4,8]). New data is regularly appearing in the literature, extending our knowledge to include many tumor sites. The evidence is now overwhelming that for most of these, local tumor control by radiotherapy is compromised in patients who are anaemic before and during radiotherapy. The role of the radiobiologist must be to offer an explanation for the clinical observations and to suggest a means of compensating for the problem in those patients whose treatment is prejudiced by anaemia. This statement assumes a cause and effect relationship between anaemia and tumor curability, supposedly through an impairment of oxygen transport to the tumor cells. We must then consider the consequences of a reduction in circulating haemoglobin levels in model tumor systems in animals, combine that information with our knowledge of physiological mechanisms and attempt to reconcile our conclusions with the clinical findings. We should be aware of course, that a failure to achieve this could be the result of inadequacies of the mouse model or because anaemia is simply not the cause of clinical radioresistance but rather a consequence, along with radiosensitivity of particular tumor characteristics. What do the experimental animal data reveal? We will consider two clinically important questions: 1) Are tumors in mice with lower than normal haemoglobin levels more resistant to radiation and what is the temporal relationship between duration of anaemia and sensitivity? 2) Does the restoration of haemoglobin levels before radiotherapy change sensitivity?

High-pressure laser photolysis study of hemoproteins. Effects of pressure on carbon monoxide binding dynamics for R- and T-state hemoglobins

The bimolecular association reaction of carbon monoxide to human adult hemoglobin at pH 7, 20 degrees C, was examined as a function of pressure up to 1500 bar by means of high-pressure laser photolysis. The apparent quantum yield for a millisecond recombination reaction decreased with pressure, which was attributed to an increase in the fraction of nanosecond geminate recombination reaction. On the basis of the pressure dependence of the recombination rate, the activation volumes at normal pressure for the binding of carbon monoxide to the R- and T-state hemoglobins were determined as -9.0 +/- 0.7 and -31.7 +/- 2.4 cm3 mol-1, respectively. Since the activation volumes for the overall CO association reaction were negative, it seems that the iron-ligand bond formation process mainly contributes to the rate-limiting step for both quaternary structures. The characteristic pressure dependence of the activation volume was observed for the R-state Hb but not for the T-state Hb. At 1000 bar, the activation volume for the R-state Hb was reduced to nearly zero, probably resulting from the contribution of the ligand migration process to the rate-limiting step. The effect of pressure on the activation enthalpy and entropy was also extracted from the data.

Structural and functional significance of inhomogeneous line broadening of band III in hemoglobin and Fe-Mn hybrid hemoglobins

Near-infrared spectra of hemoglobin and Fe-Mn hybrid hemoglobins have been obtained at cryogenic temperatures. The charge-transfer (a2u(pi)----dzy) transition at approximately 760 nm (band III) has been found to be a conformationally sensitive indicator of the heme-pocket geometry in these species. Temperature, protein tertiary and quaternary structure, chain heterogeneity, and ligand rebinding subsequent to CO photolysis all affect the line width and position of this transition. We conclude that the overall line shape of band III is derived from both subunit heterogeneity and conformational disorder within each subunit. A model is suggested that relates the observed pH dependence of the kinetic hole burning due to ligand rebinding to specific structural parameters of the proximal heme pocket that influence both the peak position and the inhomogeneous line shape of band III.

A multipass cuvette for laser photolysis studies and its uses in studying hemoglobin kinetics and equilibria

A simple multipass cuvette was constructed by cementing small first-surface mirrors to opposite optical faces of a standard cuvette, eliminating the need for complex alignment devices. The multipass cuvette could then be positioned to provide optical path lengths of approximately 5 and 7 cm for the observing beam directed perpendicularly to the laser photolytic pulse. Internal reflection losses in the cuvette elevated the baseline by 0.36 in absorbance for the seven-pass alignment. Heme proteins can easily be studied at 100 nM in this cuvette. Analysis of the concentration dependence of the rapid recombination phase following photolysis of HbCO allows KTD to be determined. Precise determination of this constant, however, requires that a large range of concentrations be studied, allowing the fraction of rapid phase to vary from 20 to 80%. Human HbCO at pH 7 cannot be effectively studied over this concentration range in ordinary cuvettes owing to the low concentrations required. By employing the multipass cuvette, we have been able to make very precise determinations of this constant and find at pH 7, 21 degrees C, a value for KTD of 0.66 microM. We also determined that the quantum yield for photolysis of HbCO dimers and tetramers must be very nearly the same. For HbCO in Tris buffer, pH 7.4, the R----T conformation change is some six to seven times slower than that in phosphate. We have developed a simple equation that allows both the rate constant for the conformational change and the KTD to be determined under these conditions. The KTD obtained is in excellent agreement with a reported value obtained by large-zone gel filtration.

Radiation induced blood pathology in chick-erythrocytes and related parameters

White leghorn male chicks at 15 days post-hatching were subjected to acute (2.10 Gy and 6.60 Gy) and fractionated (2 x 2.10 Gy) whole body gamma radiation exposure at the high dose rate of 0.60 Gy/sec to study the nature of haematological changes induced in the animals which were maintained for a maximum period of 60 days post irradiation. The investigated parameters include total red blood cell counts, haemoglobin content, haematocrit value, mean corpuscular volume and mean corpuscular haemoglobin concentration values. The results show that the haematological changes induced with 2.10 Gy and 2 x 2.10 Gy fractionated dosage are reversible and do not cause permanent damage to the erythroid characteristics. However, the system failed to recover with 6.60 Gy whole body acute exposure.

Effect of long wave u.v. irradiation on the affinity of haemoglobin for oxygen

Changes in the slope of haemoglobin-oxygen dissociation curve and its position were studied before and after the influence of long wave u.v. irradiation. Haemoglobin showed a lower than normal affinity for oxygen when exposed to 5.45 x 10(-3) J/cm2 and to lesser extent to doses of 10.90 x 10(-3) J/cm2. The elevation in P50 (representing PO2 at which Hb is half saturated) at these doses is mainly due to the new acidic groups which, by unfolding of this globular protein, become exposed in its surface. The fall in P50 at relatively high doses was found as a result of methaemoglobin increase and the partial dissociation of Hb tetramer to dimer and monomer.

[Mechanism of porphyrin conformational changes of hemoglobin in the blood in malarial infestation]

The reversible conformational changes in porphirine of hemoglobin of mouse blood during malaria and under laser and tocopherol effects were studied by means of Raman spectroscopy.

[The effect of excessive artificial UV radiation on the measurement of blood parameters and phagocytosis in calves]

5 calves of an age of 33 days were exposed to UV-light (280-320 nm) for a time of 12 hours. The mean dose of radiation was 179 x 10(-10) J/h x m-2. The results show slight influences of overdosed radiation on hemoglobin content of the blood, from 105.1 g/l to 102.6 g/l. The mean content of hemoglobin in erythrocytes decreased: 364 g/l to 347 g/l. The total leucocytes decreased from 7.74 x 10(9)/1 to 7.08 x 10(9)/1 after exposition of 5 hours. The exposition increased lymphocytes (55.6% to 66.0%) and decreased neutrophils (43.6% to 33.8%). The relationship of lymphocytes to neutrophils extended even after radiation time of only 5 hours from 1.45 to 2.04. The phagocytotic activity increased after 5 hours of exposition. To the end of exposition (60 hours after observation) a decrease was observed. A correlation between doses of radiation and hematological changes was found after 12 hours of radiation in lymphocyte counts (r = 0.878) and neutrophil counts (r = -0.824) as well as in the relation of lymphocytes to neutrophils counts (r = 0.941) and in the index of phagocytosis (r = 0.804).

Picosecond absorption studies on the photodissociation of alpha- and beta-nitrosyl hemoglobin monomers

Transient absorption studies of the pump-probe type were performed on the NO forms of the alpha- and beta-monomers of hemoglobin using a Nd3+ phosphate-glass laser. A second harmonic 531-nm, 8-ps fwhm pulse pumped the Q-band while a delayed continuum generated pulse was used to monitor pi pi* Soret absorption changes in the 410-453-nm region. Photodissociation of nitrosyl alpha- and beta-monomers was found to differ markedly from the tetramer in what we believe to be the formation of a five-coordinate HbNO (with proximal imidazole detached) photoproduct within the first 50 ps after photon absorption.

A simple method for preparation of molecular weight marker proteins for sodium dodecyl sulfate-polyacrylamide gel electrophoresis by photopolymerizations of hemoglobin subunits

Photoirradiation of globin, obtained from human hemoglobin, in the presence of oxygen and protoporphyrin produced a series of polymers of globin subunits ranging from dimer to dodecamer. These polymers are useful as molecular weight markers because they cover a relatively wide range of molecular weights (Mr 15,500-186,000) with a constant and narrow interval of Mr 15,500.

Differentiating the effects of microwave and heat on tissue proteins and their crosslinking by formaldehyde

Alkaline phosphatase activity in mouse liver blocks, cooled by an ice-bath, decreased by 50% in 5 min of microwave irradiation (280 W). This loss of protein tertiary structure has been mirrored by ultrastructural changes in the same tissue. Microwave irradiation did not produce cleavage or polymerization of lysozyme or haemoglobin. Protein formaldehyde reaction mixtures produced protein polymers between 0 degree and 40 degrees C which could be separated by SDS-polyacrylamide gel electrophoresis. Microwave irradiation of lysozyme or haemoglobin plus formaldehyde on ice-bath up to 30 min produced a similar electrophoretic pattern. When lysozyme or haemoglobin plus formaldehyde was heated to 60 degrees C for 30 min, the protein polymers migrated faster on electrophoresis, suggesting a smaller hydrodynamic volume than expected due to intramolecular crosslink formation, not opened up under the conditions of electrophoresis.