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The pulsed-field-gradient (PFG) [sup.31]P NMR diffusion spectra were measured under varied sample conditions to characterize the low-affinity binding of adenosine 5'-triphosphate (ATP) on human serum albumin (HSA) or bovine serum albumin (BSA). The NMR diffusion constants of ATP, ATP-HSA, or ATP-BSA were illustrated as function of ATP concentrations. The binding curves of ATP-HSA and ATP-BSA were identical but strikingly different from the ATP curve. Using a 'Scatchard plot', the apparent binding constant (K) and number of ATP binding sites (n) on serum albumin were evaluated as K = 75.25 [(mol/L).sup.-1] and n = 10, respectively. At a pH < 5.0 and a pH > 9.0 or a temperature > 45 °C, the diffusion data of ATP-HSA were found to increase remarkably, suggesting that the dissociation of ATP from HSA was largely enhanced, probably because of pH- or heat-induced protein structural change, degradation, or aggregation. In addition, our data indicated that ADP was strongly competitive with ATP for the low-affinity binding to HSA, but heptanone and [Cl.sup.-] were essentially noncompetitive. These results are important for further elucidating the interaction of ATP with serum albumin and its possible effect on related bioprocesses. The method can be well applied to study the binding of other nucleotides/nucleosides on proteins. Key words: NMR, [sup.31]P, ATP, serum albumin, affinity, diffusion. Operant des diverses conditions de l'echantillon, on a mesure les spectres de diffusion de RMN du [sup.31]P par la methode du gradient de champ pulse (GCP) dans le but de caracteriser la faible affinite de fixation du 5'-triphosphate d'adenosine (TPA) sur de l'albumine serique humaine (ASH) ou de l'albumine serique bovine (ASB). Les constantes de diffusion de RMN du TPA et des agregats TPA-ASH et TPA-ASB sont illustrees en fonction des concentrations du TPA. Les courbes de fixation des agregats TPA-ASH et TPA-ASB sont identiques, mais ils different beaucoup de la courbe du TPA. Faisant appel a la << courbe de Scatchard >>, on a determine que la constante apparente de fixation (K) et le nombre des sites de fixation (n) du TPA sur l'albumine serique sont respectivement de K = 75,25 [(mol/L).sup.-1] et n = 10. A un pH < 5,0 et a un pH > 9,0 ou une temperature > 45 °C, on a observe que les donnees de diffusion pour de l'agregat TPA-ASH augmentent d'une facon remarquable, ce qui suggere que la dissociation du TPA de l'ASH est fortement augmentee, probablement en raison de degradations, d'agregations ou changements structuraux dans la proteine induits par le pH ou la chaleur. De plus, nos donnees suggerent que le diphosphate d'adenosine (DPA) offre une grande competition au TPA pour la fixation de faible affinite avec l'ASH, mais que l'heptanone et l'ion [Cl.sup.-] ne sont pas en competition. Ces resultats sont importants pour une elucidation ulterieure de l'interaction du TPA avec l'albumine serique et des ses effets potentiels sur les bioprocessus apparentes. La methode peut facilement etre appliquee a l'etude de la fixation d'autres nucleotides/nucleosides sur des proteines. Mots-cles: RMN, [sup.31]P, TPA, albumine serique, affinite, diffusion. [Traduit par la Redaction], Introduction Human serum albumin (HSA) is a most abundant protein in blood plasma. It serves as a storage and transport protein for a variety of substances, such as drugs, hormones, [...]

ABSTRACT Porphyrins are a group of tetrapyrrole pigments. Physical and chemical properties of porphyrins are often related to their compositions and structures. We conducted [.sup.1]H solution NMR and UV-visible spectral [...]

Objective: This study aimed to investigate and analyze the anatomic characteristics of the retromaxillary cell (RMC) by using computed tomography (CT) images of paranasal sinuses and to improve its identification with ethmomaxillary sinus (EMS). Methods: The paranasal sinus CT scans of 441 outpatients or inpatients in our hospital from January 2018 to October 2018 were analyzed. The incidence of RMC, EMS, Haller cell, imaging anatomical characteristics, and morphological manifestations were observed via sinus CTs. The relationship of RMC and ipsilateral maxillary sinusitis was analyzed. Results: The incidence of RMC is 83.90% (740/882). The incidence of males and females was 83.81% (414/494) and 84.02% (326/388), respectively. The incidence of bilateral (72.79%, 321/441) was much higher than that of unilateral (22.22%, 98/441). The lateral extension of the RMC ranged from 1.18 to 13.31 mm, with an average of 6.10 ± 2.03 mm. The incidence of ipsilateral maxillary sinus opacification on the RMC sides and non-RMC sides has no significance difference (χ2 =.054, P =.459). The incidence of Haller cell and EMS decreased significantly in the presence of RMC (P <.01). Conclusion: The RMC is an anatomical variation originating from posterior ethmoid cells, which is commonly encountered in the clinic. The pneumatization of RMC is highly variable, and a bilateral is common. During endoscopic sinus surgery, it is necessary to carefully identify such an air cell to ensure the complete opening of the paranasal sinus during surgery. [ABSTRACT FROM AUTHOR]

ABSTRACT Guanosine 5'-triphosphate (GTP) plays a pivotal role in many biological processes. The interactions of cations with GTP are essential to the stabilization of this nucleotide and the regulation of [...]

The pulsed-field-gradient (PFG) 31P NMR diffusion spectra were measured under varied sample conditions to characterize the low-affinity binding of adenosine 5′-triphosphate (ATP) on human serum albumin (HSA) or bovine serum albumin (BSA). The NMR diffusion constants of ATP, ATP-HSA, or ATP-BSA were illustrated as function of ATP concentrations. The binding curves of ATP-HSA and ATP-BSA were identical but strikingly different from the ATP curve. Using a 'Scatchard plot', the apparent binding constant ( K) and number of ATP binding sites ( n) on serum albumin were evaluated as K = 75.25 (mol/L)-1 and n = 10, respectively. At a pH < 5.0 and a pH > 9.0 or a temperature > 45 °C, the diffusion data of ATP-HSA were found to increase remarkably, suggesting that the dissociation of ATP from HSA was largely enhanced, probably because of pH- or heat-induced protein structural change, degradation, or aggregation. In addition, our data indicated that ADP was strongly competitive with ATP for the low-affinity binding to HSA, but heptanone and Cl- were essentially noncompetitive. These results are important for further elucidating the interaction of ATP with serum albumin and its possible effect on related bioprocesses. The method can be well applied to study the binding of other nucleotides/nucleosides on proteins. [ABSTRACT FROM AUTHOR]

We conducted 31P NMR kinetic studies and 1H-diffusion measurements on myosin-catalyzed hydrolysis of adenosine triphosphate (ATP) under varied conditions. The data elucidate well the overall hydrolysis rate and various factors that significantly impact the reaction. We found that the enzymatic hydrolysis of ATP to adenosine diphosphate (ADP) was followed by ADP hydrolysis, and different nucleotides such as ADP and guanosine triphosphate acted as competitors of ATP. Increasing ATP or Mg2+ concentration resulted in decreased hydrolysis rate, and such effect can be related to the decrease of ATP diffusion constants. Below 50 °C, the hydrolysis was accelerated by increasing temperature following the Arrhenius’ law, but the hydrolysis rate was significantly lowered at higher temperature (~60 °C), due to the thermal–denaturation of myosin. The optimal pH range was around pH 6–8. These results are important for characterization of myosin-catalyzed ATP hydrolysis, and the method is also applicable to other enzymatic nucleotide reactions. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to investigate and analyze the anatomic characteristics of the retromaxillary cell (RMC) by using computed tomography (CT) images of paranasal sinuses and to improve its identification with ethmomaxillary sinus (EMS)., Methods: The paranasal sinus CT scans of 441 outpatients or inpatients in our hospital from January 2018 to October 2018 were analyzed. The incidence of RMC, EMS, Haller cell, imaging anatomical characteristics, and morphological manifestations were observed via sinus CTs. The relationship of RMC and ipsilateral maxillary sinusitis was analyzed., Results: The incidence of RMC is 83.90% (740/882). The incidence of males and females was 83.81% (414/494) and 84.02% (326/388), respectively. The incidence of bilateral (72.79%, 321/441) was much higher than that of unilateral (22.22%, 98/441). The lateral extension of the RMC ranged from 1.18 to 13.31 mm, with an average of 6.10 ± 2.03 mm. The incidence of ipsilateral maxillary sinus opacification on the RMC sides and non-RMC sides has no significance difference (χ 2 = .054, P = .459). The incidence of Haller cell and EMS decreased significantly in the presence of RMC ( P < .01)., Conclusion: The RMC is an anatomical variation originating from posterior ethmoid cells, which is commonly encountered in the clinic. The pneumatization of RMC is highly variable, and a bilateral is common. During endoscopic sinus surgery, it is necessary to carefully identify such an air cell to ensure the complete opening of the paranasal sinus during surgery.

Porphyrins are a group of tetrapyrrole pigments. Physical and chemical properties of porphyrins are often related to their compositions and structures. We conducted 1 H solution NMR and UV-visible spectral analysis to characterize the structural feature of a water-soluble, synthetic porphyrin i.e. tetrakis (p-sulfonatophenyl) porphyrin, TPPS 4 , and its interaction with different metal ions in aqueous solutions. The results indicate that tetrapyrrole and tetraphenyl rings in TPPS 4 molecule form a co-planar electron conjugation system; transition-metal ions show stronger binding capacity than alkali and alkali-earth metal ions; the relative stabilities of TPPS 4 -metal ion complexes can be well assessed by NMR and UV-visible spectral data.