Passage
Hemophilia B is a blood clotting disorder caused by a factor IX (FIX) deficiency. FIX is a 57-kDa, vitamin K-dependent protease that activates factor X, leading to the conversion of prothrombin to thrombin for propagation of the clotting cascade. Activated FIX has two major domains: a γ-carboxyglutamic acid domain and a serine protease domain. The γ-carboxyglutamic acid domain participates in the oxidation of vitamin K using metallic cofactors, as shown in Figure 1.
Figure 1 Oxidation of vitamin KTo further analyze the γ-carboxyglutamic acid-rich domain of FIX, an analogous synthetic peptide composed of matching residues 1 through 49 on FIX was evaluated by proton nuclear magnetic resonance (NMR) spectroscopy. Analysis of the proton chemical shift before the addition of metal ions suggested that the synthetic peptide contained normal structural elements. Large chemical shifts were observed after the addition of calcium and beryllium, as shown in Figure 2.
Figure 2 Results of NMR spectroscopy (tetramethylsilane [TMS] peak has been removed) The synthetic analog was then placed in solution with vitamin K hydroquinone and cofactors required for vitamin K oxidation. The oxidation products of vitamin K in Reactions 1 and 2 were collected and evaluated under high-performance liquid chromatography (HPLC) using hexane as the mobile phase. Analysis demonstrated cis and trans isomers of vitamin K₁ and a trans-epoxy vitamin K₁, as shown in Figure 3.
Figure 3 Results of HPLC separation
Adapted from Freedman SJ, Furie BC, Furie B, Baleja JD. Structure of the metal-free gamma-carboxyglutamic acid-rich membrane binding region of factor IX by two-dimensional NMR spectroscopy. J Biol Chem. 1995.
-In Reaction 1, what hybridization state changes do the methylated carbon atom in the ringed structure of vitamin K hydroquinone and the oxygen atom involved in epoxide formation undergo?

Question

Passage
Hemophilia B is a blood clotting disorder caused by a factor IX (FIX) deficiency. FIX is a 57-kDa, vitamin K-dependent protease that activates factor X, leading to the conversion of prothrombin to thrombin for propagation of the clotting cascade. Activated FIX has two major domains: a γ-carboxyglutamic acid domain and a serine protease domain. The γ-carboxyglutamic acid domain participates in the oxidation of vitamin K using metallic cofactors, as shown in Figure 1.

Figure 1 Oxidation of vitamin KTo further analyze the γ-carboxyglutamic acid-rich domain of FIX, an analogous synthetic peptide composed of matching residues 1 through 49 on FIX was evaluated by proton nuclear magnetic resonance (NMR) spectroscopy. Analysis of the proton chemical shift before the addition of metal ions suggested that the synthetic peptide contained normal structural elements. Large chemical shifts were observed after the addition of calcium and beryllium, as shown in Figure 2.

Figure 2 Results of NMR spectroscopy (tetramethylsilane [TMS] peak has been removed) The synthetic analog was then placed in solution with vitamin K hydroquinone and cofactors required for vitamin K oxidation. The oxidation products of vitamin K in Reactions 1 and 2 were collected and evaluated under high-performance liquid chromatography (HPLC) using hexane as the mobile phase. Analysis demonstrated cis and trans isomers of vitamin K₁ and a trans-epoxy vitamin K₁, as shown in Figure 3.

Figure 3 Results of HPLC separation
Adapted from Freedman SJ, Furie BC, Furie B, Baleja JD. Structure of the metal-free gamma-carboxyglutamic acid-rich membrane binding region of factor IX by two-dimensional NMR spectroscopy. J Biol Chem. 1995.
-In Reaction 1, what hybridization state changes do the methylated carbon atom in the ringed structure of vitamin K hydroquinone and the oxygen atom involved in epoxide formation undergo?

Quizplus · Accepted Answer

11ecba2d_1253_d017_a3bf_a968aa19025a_MD0008_00 Hybrid orbital theory is used to explain molecular geometry and the bonding of atomic orbitals into molecular orbitals. It states that the electrons not involved in pi bonds (p orbitals) are fused into mixed hybrid orbitals, or electron domains. Hybrid orbitals average the characteristics of s and p orbitals, and lead to orbitals with equivalent energy and shape. To determine atom hybridization, count the number of electron domains by adding up the number of lone electron pairs and sigma bonds involving the atom of interest. (Recall that double and triple bonds both include one sigma bond.) The resulting number corresponds to the number of hybrid orbitals. The sum of s and p superscripts on the hybrid name should match this number: sp³-, sp²-, and sp-hybridized atoms have four, three, and two electron domains, respectively. The superscript of 1 is implied when there is none present. The methylated carbon atom on vitamin K hydroquinone has three sigma bonds (sp²) and becomes sp³ with four sigma bonds when the epoxide is formed. The oxygen atom (from O₂) has one sigma bond and two lone pairs of electrons (sp²). The epoxide oxygen atom on vitamin K 2,3-epoxide has two sigma bonds and two lone pairs of electrons (sp³). (Choice B) The oxygen atom (O₂) is sp² hybridized rather than sp because it has one sigma bond and two lone pairs. (Choice C) The oxygen atom changes hybridization states, going from sp² to sp³. (Choice D) The methylated carbon atom in vitamin K hydroquinone is sp² hybridized because it has three sigma bonds rather than two sigma bonds (sp). This carbon atom becomes sp³ when the epoxide forms because it now has four sigma bonds. Educational objective: Hybrid orbital theory combines bound atomic orbitals into mixed hybrid orbitals of equivalent energy and shape. To determine an atom's hybridization, count the number of lone electron pairs and sigma bonds. The resulting number corresponds with the number of hybrid orbitals or electron domains.

Passage Hemophilia B Is a Blood Clotting Disorder Caused by a a Factor