Lipid vesicles penetrate into intact skin owing to the transdermal osmotic gradients and hydration force.

Hemoglobin (Hb) occurs in all the kingdoms of living organisms. Its distribution is episodic among the nonvertebrate groups in contrast to vertebrates. Nonvertebrate Hbs range from single-chain globins found in bacteria, algae, protozoa, and plants to large, multisubunit, multidomain Hbs found in nematodes, molluscs and crustaceans, and the giant annelid and vestimentiferan Hbs comprised of globin and nonglobin subunits. Chimeric hemoglobins have been found recently in bacteria and fungi. Hb occurs intracellularly in specific tissues and in circulating red blood cells (RBCs) and freely dissolved in various body fluids. In addition to transporting and storing O2 and facilitating its diffusion, several novel Hb functions have emerged, including control of nitric oxide (NO) levels in microorganisms, use of NO to control the level of O2 in nematodes, binding and transport of sulfide in endosymbiont-harboring species and protection against sulfide, scavenging of O2 in symbiotic leguminous plants, O2sensing in ...

Nonvertebrate Hemoglobins: Functions and Molecular Adaptations

Rebinding and relaxation in the myoglobin pocket

Efficient detection of paramagnetically shifted NMR resonances by optimizing the WEFT pulse sequence

Hemoglobins of the Lucina pectinata/bacteria symbiosis. I. Molecular properties, kinetics and equilibria of reactions with ligands.

Proton nuclear nagnetic resonance characterization of heme disorder in monomeric insect hemoglobins.

Assignment of proximal histidyl imidazole exchangeable proton NMR resonances to individual subunits in hemoglobins A, Boston, Iwate and Milwaukee☆

Acid Bohr effects in myoglobin characterized by proton NMR hyperfine shifts and oxygen binding studies

The monomeric insect (Chironomus thummi thummi) haemoglobins CTT III and CTT IV show an alkaline Bohr effect. The amplitude of the Bohr effect curve of CTT IV is about twice as large as that of CTT III. In particular, at low pH a time-dependent 'slow' decrease in p50 upon cyclic oxygenation/deoxygenation is observed which is larger if dithionite, instead of ascorbate, is the reducing agent. The decrease of p50 (increase in affinity) correlates with the ratio of haem-rotational components exhibiting an increase of the 'myoglobin-like' haem-rotational component with high O2 affinity and high stability of the globin-haem complex. The replacement of protohaem IX by mesohaem IX and deuterohaem IX, respectively, causes an increase in O2 affinity following the order: proto less than meso less than deutero CTT Hbs. The Bohr effect, however, seems not to be affected by these porphyrin side-group substitutions. The O2 affinity is modulated by steric effects due to the substituents in position 2 and 4 via variation of the protein-haem interactions which influence the O2 release. The replacement of iron by cobalt in proto and meso CTT IV leads to an increase of the p50 by two to three orders of magnitude. Neither central metal nor vinyl replacement affect the Bohr effect. The natural CTT Hbs III and IV analyzed for mono-componential kinetic systems exhibit pH-dependent O2 off-rate constants: 300 s-1 (at pH 5.6) and 125 s-1 (at pH 9.7) for CTT III, and 550 s-1 (at pH 5.4) and 100 s-1 (at pH 9.0) for CTT IV. Inflection points and amplitudes of the log koff/pH plots correspond to those obtained from the Bohr effect curves indicating again a larger Bohr effect for CTT IV than for CTT III. In contrast, the O2 on-rate constants are pH-independent (kon = 1.15-1.26 X 10(8) M-1 s-1). Thus, the Bohr effect is completely controlled by the off-rate constants. Analysis for bi-componential kinetic systems employing the eigenfunction expansion method clearly identifies two kinetic components for proto-IX and deutero-IX CTT Hbs which can be attributed to the two haem-rotational components x and y (x and y differ due to an 180 degree rotation of the haem group about the alpha,gamma-meso axis; y is the myoglobin-like haem-rotational component).(ABSTRACT TRUNCATED AT 400 WORDS)

Bohr effect in monomeric insect haemoglobins controlled by O2 off-rate and modulated by haem-rotational disorder

The dioxygen affinity of Dicrocoelium dendriticum haemoglobin was determined as a function of pH with a thin-layer diffusion technique. From the oxygen dissociation and association curves Hill coefficients h equal 1 were obtained throughout. Ultracentrifugation studies prove this haemoglobin to be monomeric irrespective of pH and ligation state. Thus, Dicrocoelium haemoglobin is a non-cooperative monomer. It has the highest O2 affinity so far known for any monomeric haemoglobin: its half-saturation pressure, p50 value, ranges at 25°C from 0.016 mm Hg to 0.15 mm Hg (2.13–20.0 Pa) dependent on pH. Dicrocoelium haemoglobin shows an acid Bohr effect only and as such it constitutes a new class of haemoglobins. Its log p50 versus pH plot (Bohr effect curve) is characterized by a large amplitude, Δlog p50= 0.96, and an inflection point (Bohr effect pK) at pH 5.0. A model for the acid Bohr effect of D. dendriticum haemoglobin is proposed. By generalization, both the alkaline and the acid Bohr effect in various monomeric haemoglobins may arise from a single Bohr group complex (salt bridge).

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1986.tb09481.x

Hinrich Sick

Papers

Proton nuclear nagnetic resonance characterization of heme disorder in monomeric insect hemoglobins.

Assignment of proximal histidyl imidazole exchangeable proton NMR resonances to individual subunits in hemoglobins A, Boston, Iwate and Milwaukee☆

Acid Bohr effects in myoglobin characterized by proton NMR hyperfine shifts and oxygen binding studies

Bohr effect in monomeric insect haemoglobins controlled by O2 off-rate and modulated by haem-rotational disorder

Acid Bohr effect of a monomeric haemoglobin from Dicrocoelium dendriticum. Mechanism of the allosteric conformation transition.