diff --git a/docs/model.md b/docs/model.md
index e08cff7..dc635b1 100644
--- a/docs/model.md
+++ b/docs/model.md
@@ -75,8 +75,8 @@ This page provides comprehensive information about the structure and components
 
 
 ## Ontologies
-- [schema](https://schema.org/)
 - [OBO](http://purl.obolibrary.org/obo/)
+- [schema](https://schema.org/)
 
 
 ## Types
@@ -497,12 +497,7 @@ __species_id__* `string`
 - The identifier for the described reactant.
 
 
-__init_conc__* `float`
-
-- Initial concentration of the measurement data. This must be the same as the first data point in the
-
-
-__conc_unit__* [`UnitDefinition`](#unitdefinition)
+__data_unit__* [`UnitDefinition`](#unitdefinition)
 
 - SI unit of the data that was measured.
 
@@ -517,9 +512,14 @@ __data_type__* `string`
 - Type of data that was measured (e.g. concentration)
 
 
-__prep_conc__ `float`
+__prepared__ `float`
+
+- Amount of the reactant before the measurement. This field should be used for specifying the prepared amount of a species in the reaction mix. Not to be confused with
+
+
+__initial__ `float`
 
-- Concentration of the reactant before the measurement. This field should be used for specifying the prepared concentration of a species in the reaction mix. Not to be confused with init_conc, specifying the concentration at the first data point from the
+- Initial amount of the measurement data. This must be the same as the first data point in the
 
 
 __data__* `list[float]`
diff --git a/python/pyenzyme/dataclass_models.py b/python/pyenzyme/dataclass_models.py
index e0eab13..7001626 100644
--- a/python/pyenzyme/dataclass_models.py
+++ b/python/pyenzyme/dataclass_models.py
@@ -721,11 +721,11 @@ class Measurement:
     def add_to_species_data(
         self,
         species_id: str,
-        init_conc: float,
-        conc_unit: UnitDefinition,
+        data_unit: UnitDefinition,
         time_unit: UnitDefinition,
         data_type: str,
-        prep_conc: Optional[float] = None,
+        prepared: Optional[float] = None,
+        initial: Optional[float] = None,
         data: list[float] = [],
         time: list[float] = [],
         is_simulated: bool = False,
@@ -733,11 +733,11 @@ def add_to_species_data(
     ):
         params = {
             "species_id": species_id,
-            "init_conc": init_conc,
-            "conc_unit": conc_unit,
+            "data_unit": data_unit,
             "time_unit": time_unit,
             "data_type": data_type,
-            "prep_conc": prep_conc,
+            "prepared": prepared,
+            "initial": initial,
             "data": data,
             "time": time,
             "is_simulated": is_simulated,
@@ -755,11 +755,13 @@ def add_to_species_data(
 @dataclass
 class MeasurementData:
     species_id: str
-    init_conc: float
-    conc_unit: UnitDefinition
+    data_unit: UnitDefinition
     time_unit: UnitDefinition
     data_type: str
-    prep_conc: Optional[float] = field(
+    prepared: Optional[float] = field(
+        default=None, metadata=config(exclude=lambda x: x is None)
+    )
+    initial: Optional[float] = field(
         default=None, metadata=config(exclude=lambda x: x is None)
     )
     data: List[float] = field(default_factory=list)
diff --git a/python/pyenzyme/pydantic_models.py b/python/pyenzyme/pydantic_models.py
index e73eff9..9c3b412 100644
--- a/python/pyenzyme/pydantic_models.py
+++ b/python/pyenzyme/pydantic_models.py
@@ -104,8 +104,8 @@ class EnzymeMLDocument(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "name": "schema:title",
             "references": {
                 "@id": "schema:citation",
@@ -505,8 +505,8 @@ class Creator(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "given_name": "schema:givenName",
             "family_name": "schema:familyName",
             "mail": "schema:email",
@@ -603,8 +603,8 @@ class Vessel(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@id": "schema:identifier",
                 "@type": "@id",
@@ -708,8 +708,8 @@ class Protein(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@type": "@id",
             },
@@ -821,8 +821,8 @@ class Complex(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@id": "schema:identifier",
                 "@type": "@id",
@@ -929,8 +929,8 @@ class SmallMolecule(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@id": "schema:identifier",
                 "@type": "@id",
@@ -1040,8 +1040,8 @@ class Reaction(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@id": "schema:identifier",
                 "@type": "@id",
@@ -1168,8 +1168,8 @@ class ReactionElement(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "species_id": {
                 "@type": "@id",
             },
@@ -1269,8 +1269,8 @@ class Equation(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "species_id": {
                 "@type": "@id",
             },
@@ -1430,8 +1430,8 @@ class Parameter(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@id": "schema:identifier",
                 "@type": "@id",
@@ -1533,8 +1533,8 @@ class Measurement(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@id": "schema:identifier",
                 "@type": "@id",
@@ -1625,11 +1625,11 @@ def add_type_term(
     def add_to_species_data(
         self,
         species_id: str,
-        init_conc: float,
-        conc_unit: UnitDefinition,
+        data_unit: UnitDefinition,
         time_unit: UnitDefinition,
         data_type: str,
-        prep_conc: Optional[float] = None,
+        prepared: Optional[float] = None,
+        initial: Optional[float] = None,
         data: list[float] = [],
         time: list[float] = [],
         is_simulated: bool = False,
@@ -1637,11 +1637,11 @@ def add_to_species_data(
     ):
         params = {
             "species_id": species_id,
-            "init_conc": init_conc,
-            "conc_unit": conc_unit,
+            "data_unit": data_unit,
             "time_unit": time_unit,
             "data_type": data_type,
-            "prep_conc": prep_conc,
+            "prepared": prepared,
+            "initial": initial,
             "data": data,
             "time": time,
             "is_simulated": is_simulated,
@@ -1661,11 +1661,11 @@ class MeasurementData(BaseModel):
     )  # type: ignore
 
     species_id: str
-    init_conc: float
-    conc_unit: UnitDefinition
+    data_unit: UnitDefinition
     time_unit: UnitDefinition
     data_type: str
-    prep_conc: Optional[float] = Field(default=None)
+    prepared: Optional[float] = Field(default=None)
+    initial: Optional[float] = Field(default=None)
     data: list[float] = Field(default_factory=list)
     time: list[float] = Field(default_factory=list)
     is_simulated: bool = False
@@ -1685,8 +1685,8 @@ class MeasurementData(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "species_id": {
                 "@type": "@id",
             },
@@ -1786,8 +1786,8 @@ class UnitDefinition(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
         },
     )
 
@@ -1916,8 +1916,8 @@ class BaseUnit(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
         },
     )
 
@@ -2011,8 +2011,8 @@ class EqVariable(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@type": "@id",
             },
@@ -2110,8 +2110,8 @@ class EqParameter(BaseModel):
         serialization_alias="@context",
         default_factory=lambda: {
             "enzml": "http://www.enzymeml.org/v2/",
-            "schema": "https://schema.org/",
             "OBO": "http://purl.obolibrary.org/obo/",
+            "schema": "https://schema.org/",
             "id": {
                 "@type": "@id",
             },
diff --git a/schemes/enzymeml.json b/schemes/enzymeml.json
index afbc7fc..2fa9d0e 100644
--- a/schemes/enzymeml.json
+++ b/schemes/enzymeml.json
@@ -82,62 +82,6 @@
   },
   "description": "This is the root object that composes all objects found in an EnzymeML document. It also includes general metadata such as the name of the document, when it was created/modified, and references to publications, databases, and arbitrary links to the web.",
   "definitions": {
-    "Complex": {
-      "title": "Complex",
-      "type": "object",
-      "properties": {
-        "id": {
-          "title": "id",
-          "description": "Unique identifier of the complex.",
-          "term": "schema:identifier",
-          "type": "string"
-        },
-        "name": {
-          "title": "name",
-          "term": "schema:name",
-          "type": "string"
-        },
-        "constant": {
-          "title": "constant",
-          "type": "boolean"
-        },
-        "participants": {
-          "title": "participants",
-          "description": "Array of IDs the complex contains",
-          "type": "array",
-          "items": {
-            "type": "string"
-          }
-        }
-      },
-      "description": "This object describes complexes made of reactants and/or proteins that were used or produced in the course of the experiment."
-    },
-    "Creator": {
-      "title": "Creator",
-      "type": "object",
-      "properties": {
-        "given_name": {
-          "title": "given_name",
-          "description": "Given name of the author or contributor.",
-          "term": "schema:givenName",
-          "type": "string"
-        },
-        "family_name": {
-          "title": "family_name",
-          "description": "Family name of the author or contributor.",
-          "term": "schema:familyName",
-          "type": "string"
-        },
-        "mail": {
-          "title": "mail",
-          "description": "Email address of the author or contributor.",
-          "term": "schema:email",
-          "type": "string"
-        }
-      },
-      "description": "The creator object contains all information about authors that contributed to the resulting document.",
-      "term": "schema:person"
-    },
     "Measurement": {
       "title": "Measurement",
       "type": "object",
@@ -218,6 +162,62 @@
       },
       "description": "This object describes an ordinary differential equation that is part of the kinetic model."
     },
+    "Complex": {
+      "title": "Complex",
+      "type": "object",
+      "properties": {
+        "id": {
+          "title": "id",
+          "description": "Unique identifier of the complex.",
+          "term": "schema:identifier",
+          "type": "string"
+        },
+        "name": {
+          "title": "name",
+          "term": "schema:name",
+          "type": "string"
+        },
+        "constant": {
+          "title": "constant",
+          "type": "boolean"
+        },
+        "participants": {
+          "title": "participants",
+          "description": "Array of IDs the complex contains",
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        }
+      },
+      "description": "This object describes complexes made of reactants and/or proteins that were used or produced in the course of the experiment."
+    },
+    "Creator": {
+      "title": "Creator",
+      "type": "object",
+      "properties": {
+        "given_name": {
+          "title": "given_name",
+          "description": "Given name of the author or contributor.",
+          "term": "schema:givenName",
+          "type": "string"
+        },
+        "family_name": {
+          "title": "family_name",
+          "description": "Family name of the author or contributor.",
+          "term": "schema:familyName",
+          "type": "string"
+        },
+        "mail": {
+          "title": "mail",
+          "description": "Email address of the author or contributor.",
+          "term": "schema:email",
+          "type": "string"
+        }
+      },
+      "description": "The creator object contains all information about authors that contributed to the resulting document.",
+      "term": "schema:person"
+    },
     "SmallMolecule": {
       "title": "SmallMolecule",
       "type": "object",
@@ -270,6 +270,46 @@
       },
       "description": "This object describes the reactants that were used or produced in the course of the experiment."
     },
+    "Reaction": {
+      "title": "Reaction",
+      "type": "object",
+      "properties": {
+        "id": {
+          "title": "id",
+          "description": "Unique identifier of the reaction.",
+          "term": "schema:identifier",
+          "type": "string"
+        },
+        "name": {
+          "title": "name",
+          "description": "Name of the reaction.",
+          "type": "string"
+        },
+        "reversible": {
+          "title": "reversible",
+          "description": "Whether the reaction is reversible or irreversible",
+          "type": "boolean"
+        },
+        "kinetic_law": {
+          "$ref": "#/definitions/Equation"
+        },
+        "species": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/ReactionElement"
+          }
+        },
+        "modifiers": {
+          "title": "modifiers",
+          "description": "List of reaction elements that are not part of the reaction but influence it.",
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        }
+      },
+      "description": "This object describes a chemical or enzymatic reaction that was investigated in the course of the experiment. All species used within this object need to be part of the data model."
+    },
     "Protein": {
       "title": "Protein",
       "type": "object",
@@ -363,46 +403,6 @@
       },
       "description": "This object describes vessels in which the experiment has been carried out. These can include any type of vessel used in biocatalytic experiments.",
       "term": "OBO:OBI_0400081"
-    },
-    "Reaction": {
-      "title": "Reaction",
-      "type": "object",
-      "properties": {
-        "id": {
-          "title": "id",
-          "description": "Unique identifier of the reaction.",
-          "term": "schema:identifier",
-          "type": "string"
-        },
-        "name": {
-          "title": "name",
-          "description": "Name of the reaction.",
-          "type": "string"
-        },
-        "reversible": {
-          "title": "reversible",
-          "description": "Whether the reaction is reversible or irreversible",
-          "type": "boolean"
-        },
-        "kinetic_law": {
-          "$ref": "#/definitions/Equation"
-        },
-        "species": {
-          "type": "array",
-          "items": {
-            "$ref": "#/definitions/ReactionElement"
-          }
-        },
-        "modifiers": {
-          "title": "modifiers",
-          "description": "List of reaction elements that are not part of the reaction but influence it.",
-          "type": "array",
-          "items": {
-            "type": "string"
-          }
-        }
-      },
-      "description": "This object describes a chemical or enzymatic reaction that was investigated in the course of the experiment. All species used within this object need to be part of the data model."
     }
   }
 }
\ No newline at end of file
diff --git a/schemes/enzymeml.shex b/schemes/enzymeml.shex
index abe70a4..814188c 100644
--- a/schemes/enzymeml.shex
+++ b/schemes/enzymeml.shex
@@ -1,7 +1,7 @@
 PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
 PREFIX enzml: <http://www.enzymeml.org/v2/>
-PREFIX schema: <https://schema.org/>
 PREFIX OBO: <http://purl.obolibrary.org/obo/>
+PREFIX schema: <https://schema.org/>
 
 enzml:EnzymeMLDocument {
     schema:title xsd:string {
diff --git a/schemes/enzymeml.xsd b/schemes/enzymeml.xsd
index 18dd692..62afc51 100644
--- a/schemes/enzymeml.xsd
+++ b/schemes/enzymeml.xsd
@@ -616,14 +616,7 @@
                     </xs:documentation>
                 </xs:annotation>
             </xs:element>
-            <xs:element name="init_conc" type="xs:float">
-                <xs:annotation>
-                    <xs:documentation>
-                        Initial concentration of the measurement data. This must be the same as the first data point in the
-                    </xs:documentation>
-                </xs:annotation>
-            </xs:element>
-            <xs:element name="conc_unit" type="UnitDefinitionType">
+            <xs:element name="data_unit" type="UnitDefinitionType">
                 <xs:annotation>
                     <xs:documentation>
                         SI unit of the data that was measured.
@@ -644,10 +637,17 @@
                     </xs:documentation>
                 </xs:annotation>
             </xs:element>
-            <xs:element name="prep_conc" type="xs:float">
+            <xs:element name="prepared" type="xs:float">
+                <xs:annotation>
+                    <xs:documentation>
+                        Amount of the reactant before the measurement. This field should be used for specifying the prepared amount of a species in the reaction mix. Not to be confused with
+                    </xs:documentation>
+                </xs:annotation>
+            </xs:element>
+            <xs:element name="initial" type="xs:float">
                 <xs:annotation>
                     <xs:documentation>
-                        Concentration of the reactant before the measurement. This field should be used for specifying the prepared concentration of a species in the reaction mix. Not to be confused with init_conc, specifying the concentration at the first data point from the
+                        Initial amount of the measurement data. This must be the same as the first data point in the
                     </xs:documentation>
                 </xs:annotation>
             </xs:element>
diff --git a/typescript/src/index.ts b/typescript/src/index.ts
index 50f686c..4dc27de 100644
--- a/typescript/src/index.ts
+++ b/typescript/src/index.ts
@@ -390,27 +390,25 @@ export const MeasurementCodec = D.lazy("Measurement", () => D.struct({
     time course data.
 
     * @param species_id - The identifier for the described reactant.
-    * @param init_conc - Initial concentration of the measurement data. This must be the same
-             as the first data point in the
-    * @param conc_unit - SI unit of the data that was measured.
+    * @param data_unit - SI unit of the data that was measured.
     * @param time_unit - Time unit of the replicate.
     * @param data_type - Type of data that was measured (e.g. concentration)
-    * @param prep_conc - Concentration of the reactant before the measurement. This field
-             should be used for specifying the prepared concentration
-             of a species in the reaction mix. Not to be confused with
-             init_conc, specifying the concentration at the first data
-             point from the
+    * @param prepared - Amount of the reactant before the measurement. This field should be
+             used for specifying the prepared amount of a species in
+             the reaction mix. Not to be confused with
+    * @param initial - Initial amount of the measurement data. This must be the same as the
+             first data point in the
     * @param data - Data that was measured.
     * @param time - Time steps of the replicate.
     * @param is_simulated - Whether or not the data has been generated by simulation.
 **/
 export interface MeasurementData extends JsonLd {
   species_id: string;
-  init_conc: number;
-  conc_unit: UnitDefinition;
+  data_unit: UnitDefinition;
   time_unit: UnitDefinition;
   data_type: string;
-  prep_conc?: number | null;
+  prepared?: number | null;
+  initial?: number | null;
   data: number[];
   time: number[];
   is_simulated: boolean;
@@ -418,11 +416,11 @@ export interface MeasurementData extends JsonLd {
 
 export const MeasurementDataCodec = D.lazy("MeasurementData", () => D.struct({
     species_id: D.string,
-    init_conc: D.number,
-    conc_unit: UnitDefinitionCodec,
+    data_unit: UnitDefinitionCodec,
     time_unit: UnitDefinitionCodec,
     data_type: D.string,
-    prep_conc: D.nullable(D.number),
+    prepared: D.nullable(D.number),
+    initial: D.nullable(D.number),
     data: D.array(D.number),
     time: D.array(D.number),
     is_simulated: D.boolean,