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排序方式: 共有543条查询结果,搜索用时 15 毫秒
121.
Viroj Wiwanitkit 《Indian journal of human genetics》2013,19(3):279-281
Hemoglobin E (Hb E) disorder is an important kind of hemoglobinopathy. It can be seen around the world with the highest prevalence in Southeast Asia. The screening for this disorder becomes the public health policies in many countries. The screening can be performed in several population groups. The newborn screening program for Hb E disorder is an important issue in pediatric genetics. In this brief review, the author discusses on important laboratory tests for screening for Hb E disorder in newborn. 相似文献
122.
Birds during normal sustained flight must be able to dissipate more than 8 times as much heat as during rest in order not to be overheated. The experiments reported in this note on the hemoglobin systems from two different birds indicate the existence of a molecular mechanism by which hemoglobin is used simultaneously for oxygen transport and heat dissipation. 相似文献
123.
Eduardo Lissi 《Free radical biology & medicine》1998,24(9):1535-1536
Oxidation of oxyhemoglobin by nitrite ions to produce methemoglobin is one of the more employed procedures to oxidize the hemoprotein. The process takes place readily after a clear induction time. This behaviour is usually explained in terms of an autocatalytic reaction mechanism. However, the generally accepted mechanism is not autocatalytic and cannot explain the main features of the process. In the present work it is proposed that the characteristics of the process require the occurrence of a fast reaction between oxyhemoglobin and nitrogen dioxide. This process acts as a branching step, leading to the observed autocatalysis. 相似文献
124.
R. Bolla 《Journal of nematology》1979,11(3):250-259
Attempts to develop defined in vitro culture systems for the growth, reproduction and development of free-living nematodes have yielded much basic information about their nutritional requirements and biochemistry. Requirements for sterol and heme have been identified suggesting that some nematodes lack de novo synthesis of these molecules. Possible pathways of metabolism of these nutritional requirements can be derived from in vitro experiments that use a variety of sterol and heine sources as supplements to the culture mediuin. These pathways are reviewed as well as the possible role of sterol and heme in the biology of free-living and parasitic nematodes, Since these molecules must be acquired dietarily, the possible involvement of lysosomal enzymes in digestion is discussed. Also considered is the possibility that lysosomal enzymes change when nematodes are fed on a heine protein source. 相似文献
125.
Both negative-stain and freeze-fracture electron microscopic techniques revealed that the ultrastructure of resealed white ghosts prepared at high dilution during the hemolysis step is very different from that of resealed ghosts prepared at low or moderate dilution (pink ghosts). The negative-stained resealed white ghosts showed light halo substructures on membrane surfaces and protrusions at the edge of the ghosts. Freeze-fracturing of these ghosts showed that membrane blebbing had occurred and that fragments of the membranes resealed to form small right-side-out vesicles ranging from 0.1 to 0.3 μm in diameter. 相似文献
126.
127.
Mallory D. Salter George C. Blouin Jayashree Soman Eileen W. Singleton Sylvia Dewilde Luc Moens Alessandra Pesce Marco Nardini Martino Bolognesi John S. Olson 《The Journal of biological chemistry》2012,287(40):33163-33178
Although molecular dynamics simulations suggest multiple interior pathways for O2 entry into and exit from globins, most experiments indicate well defined single pathways. In 2001, we highlighted the effects of large-to-small amino acid replacements on rates for ligand entry and exit onto the three-dimensional structure of sperm whale myoglobin. The resultant map argued strongly for ligand movement through a short channel from the heme iron to solvent that is gated by the distal histidine (His-64(E7)) near the solvent edge of the porphyrin ring. In this work, we have applied the same mutagenesis mapping strategy to the neuronal mini-hemoglobin from Cerebratulus lacteus (CerHb), which has a large internal tunnel from the heme iron to the C-terminal ends of the E and H helices, a direction that is 180° opposite to the E7 channel. Detailed comparisons of the new CerHb map with expanded results for Mb show unambiguously that the dominant (>90%) ligand pathway in CerHb is through the internal tunnel, and the major (>75%) ligand pathway in Mb is through the E7 gate. These results demonstrate that: 1) mutagenesis mapping can identify internal pathways when they exist; 2) molecular dynamics simulations need to be refined to address discrepancies with experimental observations; and 3) alternative pathways have evolved in globins to meet specific physiological demands. 相似文献
128.
The antimicrobial activity of hemoglobin fragments (hemocidins) has been reported in a variety of models. The cattle tick Rhipicephalus (Boophilus) microplus is a blood sucking arthropod from where the first in vivo-generated hemocidin was characterized (Hb 33-61). In the present work we identified a novel antimicrobial peptide from the midgut of fully engorged R. (B.) microplus females, which comprises the amino acids 98-114 of the alpha subunit of bovine hemoglobin, and was designated Hb 98-114. This peptide was active against several yeast and filamentous fungi, although no activity was detected against bacteria up to 50μM of the synthetic peptide. Hb 98-114 was capable of permeabilizing Candida albicans cell membrane and had a fungicidal effect against this yeast. Circular dichroism (CD) and nuclear magnetic resonance (NMR) experiments showed that Hb 98-114 has a random conformation in aqueous solution but switches to an alpha-helical conformation in the presence of sodium dodecyl sulfate (SDS). This alpha helix adopts an amphipathic structure which may be the mechanism of cell membrane permeabilization. Importantly, Hb 98-114 may play an important role in defending the tick midgut against fungal pathogens and is the first hemocidin with specific antifungal activity to be characterized. 相似文献
129.
130.
G. M. Artmann Ilya Digel K. F. Zerlin Ch. Maggakis-Kelemen Pt. Linder D. Porst P. Kayser A. M. Stadler G. Dikta A. Temiz Artmann 《European biophysics journal : EBJ》2009,38(5):589-600
When aspirating human red blood cells (RBCs) into 1.3 μm pipettes (ΔP = −2.3 kPa), a transition from blocking the pipette below a critical temperature T
c = 36.3 ± 0.3°C to passing it above the T
c occurred (micropipette passage transition). With a 1.1 μm pipette no passage was seen which enabled RBC volume measurements
also above T
c. With increasing temperature RBCs lost volume significantly faster below than above a T
c = 36.4 ± 0.7 (volume transition). Colloid osmotic pressure (COP) measurements of RBCs in autologous plasma (25°C ≤ T ≤ 39.5°C) showed a T
c at 37.1 ± 0.2°C above which the COP rapidly decreased (COP transition). In NMR T1-relaxation time measurements, the T1 of RBCs in autologous plasma changed from a linear (r = 0.99) increment below T
c = 37 ± 1°C at a rate of 0.023 s/K into zero slope above T
c (RBC T1 transition). In conclusion: An amorphous hemoglobin–water gel formed in the spherical trail, the residual partial sphere
of the aspirated RBC. At T
c, a sudden fluidization of the gel occurs. All changes mentioned above happen at a distinct T
c close to body temperature. The T
c is moved +0.8°C to higher temperatures when a D2O buffer is used. We suggest a mechanism similar to a “glass transition” or a “colloidal phase transition”. At T
c, the stabilizing Hb bound water molecules reach a threshold number enabling a partial Hb unfolding. Thus, Hb senses body
temperature which must be inscribed in the primary structure of hemoglobin and possibly other proteins.
This article is dedicated to Ludwig Artmann who died on July 21, 2001 on a beautiful summer day during which we performed
experiments far away. Ludwig Artmann was a man who encouraged us to be strong and to study hard no matter what were the costs. 相似文献