Ferric species equilibrium of the giant extracellular hemoglobin of Glossoscolex paulistus in alkaline medium: HALS hemichrome as a precursor of pentacoordinate species

Ferric species of the giant extracellular hemoglobin of Glossoscolex paulistus as function of pH: An EPR study on the irreversibility of the heme transitions

“…The presence of the couple of peaks that characterizes the axial spectrum (g~6.20 and 2.00) denotes that the several species formed do not represent the total consumption of the original aquomet species, which is a characteristic inherent to the equilibria involving ferric species of hemoglobin (Svistunenko et al, 2000). Furthermore, the slight asymmetry of the intense peak encountered in g~6.0 is an evidence of an initial formation of pentacoordinate ferric heme species, in agreement with previous works Moreira et al, 2008b). This complex equilibrium is characterized by a significant presence of the species that denote more drastic protein unfolding, indicating that the stability and intensity of the presence of hemichromes and pentacoordinate species is deeply associated with the degree of spatial arrangement change of the quaternary architecture.…”

“…Likewise, it has been demonstrated that in alkaline (Moreira et al, 2008b) as well as in acid medium , the heme ferric transitions caused by more drastic pH transitions propitiate a process of secondary structure loss, which is detected by Circular Dichroism (CD), that is intrinsically related to the modifications that occur in the first sphere coordination of the ferric center.…”

“…Therefore, this sample was adjusted to pH 7.0 after a slight transition until pH 6.0. In spite of the well well-known stability of the aquomet ferric species in slightly acidic medium Moreira et al, 2008b), it is possible to detect a significant change of this spectral profile when compared with the original spectrum of the "native" aquomet species obtained at pH 7.0 (Fig. 1).…”

Photodynamic Therapy: Porphyrins and Phthalocyanines as Photosensitizers

“…[89,[147][148][149][150][151][152][153][154][155][156][157][158] For example, we can mention the different species of hemichrome (bis-histidine complex) found in ferric forms of the giant extracellular haemoglobin of Glossoscolex paulistus (HbGp), depending only on the reciprocal orientation of the same axial ligands. [159,160] Furthermore, the complexity of the autoxidation behaviour presented by this giant haemoglobin, depending on the medium conditions, denotes that the relationship between the spatial conformation of globins and the flexibility of the haem pocket is not trivial, constituting a challenging topic in the chemistry of haemoproteins. [161,162] In fact, several recent works have focussed on the structural properties of HbGp in order to contribute to the understanding of the physicochemical properties of this HbGp as well as its structure-activity relationship.…”

Bioinformatical Development of Oligonucleotides for the d Chain Gene of the Giant Extracellular Hemoglobin of Glossoscolex Paulistus

“…This can be easily observed through of its redox and structural stabilities even when submitted to storage procedures without control of the oxygen presence, i.e., without conditions of inert atmosphere. [15]. Furthermore, these hemoglobins are considered hemoprotein systems with great cooperativity, and in some cases with "supercooperativity" [16], [17].…”